The three methods I cover are:
1) Manual desoldering pump at (adafruit.com)
2) 30 Watt Electric desoldering Tool at (amazon.com) or (elexp.com)
3) Solder wick at (adafruit.com)

If you don’t care to watch the video I will summarize below.

I have an exterior timer control that turns my Christmas lights on at dusk and off after 6 hours. I noticed they never turned off one day and thought I had left the timer control set to the ON position. But no, it was set to off 6 hours after dusk. I then set the selection switch to OFF but still it was on. I unplugged and plugged it back in but got the same problem. It was time to go to the electronics bench.

CLICK TO READ ALL —>:

NO SCREWS!! Damn now I have to bust this open. That alone might mean this is not going to be fixable. A few swift whacks with a hammer along the glued seams and it popped open. NICE! If I can fix it I can glue it up and be back to its water tight condition.

The board was single sided and all through hole construction. A quick glance around the board and I spied what looked like a fried transistor wired up to turn a 15A 125VAC relay on and off. The bottom of the transistor was all bubbled and I was sure it was a dead short causing the relay to be on all the time.

Above is a close up of transistor.

I removed the bad transistor using solder wick for one leg,

desolder pump for another leg

and for the last leg I used a 30 watt electric desoldering wand. This electric desolder wand is under $30 at most places and is a super greate tool IF YOU KEEP IT CLEAN! I used these three methods just to show the video viewers how each method works. The hints I give along the way are to set your solder iron to max when using solder wick and preheat the solder before applying the wick. I have also read that adding lead based solder to the joint in advance also helps the lead free solder wick up into the braid better.

This is the plunger in the desolder wand and it needs to be cleaned often!

This stuff will get on the o-rings and keep you from having a strong solder sucking vacuum.

I demonstrate how important it is to clean desolder pumps by taking one apart and using a bottle brush to get all the old solder scrap out. Then add a little Vaseline to the o-rings before reassembling.

Finally for the electric desolder pump/wand combo you must clean the hole in the tip with a wire that comes with the tool. If you follow these tips your component removal will be easy.

After getting the transistor out I take down the component number so I could lookup if it was a PNP or NPN and what leads were emitter, collector and base in the package. With this information I use the below transistor testing image to test if the transistor is good.

Photo from: “Using Your Meter” by Alvis J. Evans at (amazon.com) I did alter this image to be easier to read and use for DMM diode mode testing.

These images are really for using an ohm meter but if you put your DMM in diode test mode you get the same test except you’re testing the PN junction between the positive and negative DDM test leads instead of a straight up resistance. Where you see “LOW” you should get a forward bias diode junction pass on your DMM indicating a very low electrical resistance and where you see “HIGH” you should get OL on your DMM meaning “open loop” junction or very high electrical resistance.

If your type of transistor, NPN or PNP, fails one of the tests in any direction then it is bad and needs to be replaced. Please note that this is not a complete electrical test of a BJT transistor. A transistor can have other issues like high leakage and in circuit modes of failure that are beyond the scope of what I want to cover here. But if it fails this simple test it is bad and you can confidently know you have to replace the transistor.

My transistor passed with flying colors! So my problem was not this transistor and closer inspection revealed the melted plastic by the component’s legs was just some glue used to seal the case.

Nothing else controls the relay on my board so it must be the relay itself. I looked up the relays datasheet on the internet and found its pin out configuration then tested between the in and out of the normally open (NO) pins.

Sure enough it was a dead short so the relay’s contact points must be fused together.

Just for a bit of fun I used my Dremel tool and cut off the plastic top of the relay to see the failure. Sure enough the points were fused.

I popped the relay’s contact points apart and cleaned them up with some metal grade sandpaper. After tested the coils I soldered it back into the circuit along with the transistor I removed.

A quick test with my radio as the load showed the timer control was now working great!

I don’t want to put the repaired controller back in service knowing the relay has already had such damage so I will order a suitable replacement the next time I make a bulk parts order. For a couple of bucks I will have my Christmas light timer control back in service and not in a landfill.

UPDATE Dec 24th 2011:

My replacement relay has arrived. I dropped it in, sealed the box with hot glue and put it back in service. It is working perfectly. I replaced the relay with a 10Amp instead of the original 15Amp but that is just fine for my Christmas lighting plus it was cheaper at just $1.75 USA. The new relay was SPDT (single pole double throw) so I had to snip off the NC (normally closed) pin.

Thanks for visiting and don’t forget to subscribe to my YouTube channel if you like my videos.

A representative from Farnell contacted me and asked if I wanted to review some products. I said, “Sure, free supplies for my lab!” Actually, I found out that anybody can sign up for their product “Road Test” program at Element14.com but not everyone is selected. Farnell is a European company and known as Element14 in Asia and Newark in America (online catalog). But they also have a nice online community site at Element14.com/Community where you can get to their “Store” for your region.

For the “Road Test” I chose to review some different test lead management hangers made by Pomona. I have quite the mess of jumpers, patch cables, DMM probes and oscilloscope probes hanging on my peg board behind my lab bench. That is not a good way to store these and they are very difficult to access on peg board.

I selected two sizes with two different mounting options for this review. The Pomona model 1508 with 14 slots at 0.21in (5.33mm) opening is great for jumpers, patch cable and test leads. The 1508 model needs to mount using screws.

<photo 1508>

I also got the Pomona model 4408M with 8 slots at 0.32in (8.13mm) opening with magnet mounting. The 4408M is nice for oscilloscope probes and larger items.

<photo 4408M>

I was quite disappointed to find that you lose two slots for the magnet mount because they just bend the outside prongs down and add stick on magnets. This magnetic option drops a model 4408 with 10 slots to a 4408M with only 8 slots. If I had known that I would have got the model 4408 and just added my own magnetic plate. The photo for 4408M at Neward.com is curretly wrong and shows the model 2708 without bent prongs.
The magnetic option was not strong enough for the thin metal in my garage door anyway so I bent the two extra prongs up and used the screw mounts.

You can fabricate your own test lead hangers but at these prices it just makes sense to buy.
1508 is $17.53 USD (at the time of writing this it is on sale for $12.46)
4408 is $14.65 USD  (at the time of writing this it is on sale for $10.43)
4408M with magnet mount is $32.13 USD  (at the time of writing this it is on sale for $23.46)

Here are the after shots of my lab. WOW these hangers sure helped clean things up and I have already found it much easier to find and select items.

I even found some lost jumpers and micro hooks. I thought they were gone forever but were just under the pile of cables hanging on my peg board. I will not be losing track of such items anymore!

I guess I will have to get one more 1508 because I have so many jumper cables. I may even get their biggest hanger model 2708 with 9 slots at 0.45in (11.43mm) opening for my PC power cords and wall warts.

Thanks for visiting.

In this write up & video I review the “GE Color Effects” G35 multi colored LED Christmas lights 50 count. I will cover product details, hanging hints and show a teardown and give some links to great hacks at the end.

You get to pick from 14 sequence patterns using a wireless controller.  Hacking these lights using Arduino is already very popular so I will be linking to some good hack posts below. In a later video I will be trying some of the known hacks and some of my own.

Link to the GE product page for these lights

In the box you get the below:

40.8 feet of lights
50 lights spaced at 10 inches
50 rain gutter clips, 50 base clips
Radio controller with 14 light patters

CLICK TO READ ALL —>:

The light patterns are labeled on the back of the remote. Very nice touch but the 14 options are not very good. They all blink or change or race too fast. I would have much preferred a softer mood with solid color options or slower changing effects.  These lights just must be hacked!

And you get a switch mode power supply 120v AC 0.4A to 5v DC 3A (later in the post I show that these rating are more than enough).

I got my lights on sale back in August at Costco for ~$60 but these 50 count lights can run from $100 to $120 on Amazon.  There are other light counts and light styles in the “GE Color Effects” product line. (See above product page link for such details).

First let’s cover hanging. I was very surprised at how much care and thought was put into the hangers, which are included. You can use the hangers in several ways, either with or without the rain gutter clips.

I don’t have rain cutters so I screwed these base snaps to the underside of my fascia boards.

It was easier for me to sit at my bench and pre-screw the 50 clips with a short pan-head screw.

I then used an 11 inch board with a nail driven though each end spaced at exactly 10 inches.  I used this jig to mark off the 10 inches between each clip.  If you use bigger nails and give the jig a whack with a hammer when marking off, you will get nice pilot holes too.

Even using this jig it was very slow going putting up 150 clips.  I experimented with other ideas and the only other option for my wood fascia board would have been to use the rain gutter clips with some staples. I found that Arrows T-25 cable staples and cable stapler worked just great. These rounded staples leave just enough room to slide the clips in and out.

I also tried square staples but they didn’t work at all. They drive too deep or too shallow and there was no good way to make the square staples work.

Between the rounded cable staples and the screws I picked the screws as seen on the right side of the below photo.

I liked the screw method because the wires are harder to see when you screw the base clips directly to the bottom of the fascia boards.

This is my house with 150 lights. Not easy taking photos in the dark. They are very bright, much brighter than you can tell in this photo. I must say I love how big and bright they are but I will have to hack these lights to get better color effects and timing.

Now let’s take some measurements and take a look inside these lights. When connected to my bench supply at 5v none of the light patterns took more than 1.75A which was solid white.  All the other patterns ran from 0.89A to 1.47A so this is way under the 3A switch mode power supply that comers with each light strand.
I can’t set all the lights to be solid but I was able to pick a slow enough race pattern that would race all the colors to one color before switching to the next color. Just as the 50 lights all got to a single color I would record the amps on my bench supply. Here is what I got.

Red 0.91A
Blue dark 1.2A
Blue light 1.4A
Green 0.89A
Purple 1.46A
Yellow 1.47A
White 1.75A

And the 120v AC amps when set to solid white for all 50 lights came to 0.209A, also way under the power supplies rating of 0.4 amps.  So these lights come with very good rated power supplies for the loads they will be powering.  This also means that running these lights is even less then I thought at 25.08 Watts.  WOW that’s less power than a single old style night light for the whole strand including the controller.

The plastic crystal defusing covers just pop right off giving you a good view of the surface mounted RGB colored LED in a sealed clear plastic case.

Here is a close up where you can see the PCB and the silk screen labeling. You can clearly see where the three wires come into each PCB. The two outside wires are for 5v power and ground and the middle wire is the data line that transmits the color codes to each LED.

Opening up the control box reveals a single sided board with a radio control daughter board on the back side. Here are some close ups.

The black blob is a “Chip on board” where they glue a chip die directly to the PCB, wire bond from the die to the PCB and then seal it all up with a blob of epoxy/resin.  It is a very cheap way to mass produce a product but I find it strange they also have a micro controller on the board.

The micro controller is the surface mount SOP-20 chip (20 pins) by MEGAWIN. Here is the datasheet. http://www.megawin.com.tw/megawin_EN/UploadFiles/MG87FEL2051_4051_6051_DS_v103.pdf

MG87FE2051AS20
Here are the specs.
MG87FE/L2051/4051/6051is single-chip 8-bits microcontroller with the instruction sets fully compatible with industrial-standard 80C51 series microcontroller.2K/4K/6Kbytes flash memory and 256 bytes RAM has been embedded to provide widely field application. In-System-Programming and In-Application-Programming allows the users to download new code or data while the microcontroller sits in the application. This device executes one machine cycle in 6 clock cycles or 12 clock cycles. MG87FE/L2051/4051/6051 has one 8-bit I/O ports (P1),one 7-bit I/O port (P30~P35,P37), two 16-bit timer/counters, one PWM-timer for 8-channel PWM output, a seven-source, four-priority-level interrupt structure, an enhanced UART, a precision analog comparator, on-chip crystal oscillator (combined P42,P43) and a high-precision internal oscillator.

Below is the radio daughter board on the back side of the main board. The unpopulated parts you see are for a crystal for the micro controller on the other side.  To save money they programmed the micro to use an internal timer instead of the quality external crystal.  If they had populated the crystal and the capacitors for the crystal on the front side then I would have had no problem synchronizing two light strands and keeping them in sync.  But with the low grade internal timer, each chip will have a different idea of time and even when you do get two strands in sync the poor internal timers will just drift and the light strands will be all out of whack with each other in under an hour.  Unfortunately you can’t just populate the crystal yourself because the micro is internally set to look at the internal timing not an external crystal, oscillator or resonator.

Under this daughter board I could see another “chip on board” so this radio board was setup for some major mass production. Under this board I can see the silk screening for a button (SW1) so this board can be used with our without the radio option.

And you can see the in the plastic over it is setup for a hole to be punched for a button. I would guess this is for other products GE sales that don’t have radio control and you just push a button to switch patterns or hold the button for a count of “?” to turn on and off.

Button hole on front cover if punched.

This would be where the button would be mounted on the PCB board if this was not a wireless model.  I was able to short these two traces with a quick flick to change patterns and a longer short did turn off the unit as I suspected.

Now for the deep hacking folks.  I wanted to take close up photos of the traces in the hope that maybe a more easily programmed SOP-20 micro could be implemented. Maybe some ATmega or PIC would be dropped on board and programmed in place keeping the board and its radio control.  The crystal and capacitors could also be populated for better timing. Then these strands can be synchronized as well as programmed with better patterns. (Click for larger photos)

If the crystal is populated on the back side here is where the legs come up. And just below you can see C1 and C2 which would be the capacitors home needed for the crystal.

I know we need to see the traces under the IC so I used my hot air wand to remove it and take photos.

Below I tracked the copper just incase it was not clear where the traces ran in the above photos.  This helps a ton being we know what connects to each and every pin of the micro controller. This is a single sided single layer board so nothing hard really.

Now the IC is back on and as you can see the lights are running fine.

That is it for my review and teardown. Now for some links to others that are doing some hacks for these lights.

DigitalMisery.com has an open source drop in wireless replace board for these lights. WOW, you can’t ask for more than that. He does not sell the boards yet but keep checking his site to see if he gets a Kick starter going or just follow his open source documents and spin your own board. He links to his code and the Arduino library’s “G35Arduino”

DeepDarc.com put up some amazing engineering details on these lights and reverse engineered both the radio protocol and the protocol used on the LED data bus. You must read his post if you’re going to be hacking these lights. He also shares his code and other very useful tips.

Keithsw has some great stuff synchronizing 6 strands and shares his control code, Arduino circuit and a PC software simulator program to help design the layout and patterns.  Here is his short (video).

CheerLights is an ioBridge Labs project that allows people all across the world to synchronize their lights. This sit gives all the hacking details and you can play along even it you don’t have lights by tweeting a color to @cheerlights and watching on ustream.

Jim at Jim’s G-35 Project Page makes his own control board using a PIC18F2620 micro controler.

If I have any of my own hack updates I will link to them from here and under “All Postings” with the title “G35 LED Christmas Light…”

First up was the solder tab type AA 1.2v Ni-Cd in my beard trimmer. I know, not the most attractive thing a man wants to see in his bathroom.

Then my programmable Christmas tree light timer which needed a coin cell 1.2v Ni-MH with PCB mounting tabs.

I noted in the video that it was interesting they were powering the timer controller using a bridge rectified AC to DC converter.  I was surprised to see this without the use of a step down transformer before the rectifier circuit.  Further research, I found this is quite common in consumer products that require less than 70mA and it can be done safely and cost effectively.  There are some pros and cons to this approach. If you want the full details with the math and picking the correct sized passive devices  you can review this nice article at Microship.com.  For the power conditioning circuit which is closes to what is in my timer see Fig.12 in the article.

In this video I share this simple hack and go into the math just enough so others can calculate the correct size light bulb for such a DC power supply hack if ever needed.

CLICK TO READ ALL —>:

I needed to cool the below electric motor with the fan from an old computer case.

This is the 12v DC fan that needs the power supply. It has 3 wires but the yellow wire will not be used because it is just for sensing RPMs.

Below is the salvaged diode from a trashed microwave oven. A smaller form factor common 1N4004 would work better if you have one handy.

This is the 470uF 80v electrolytic capacitor I used. I salvage it from a dead power supply long ago. A rating as low as 40v would work too.

In the video I cover how the AC waveform is conditioned into DC and how to calculate true RMS when working with 1/2 rectified sin waves; which is peak voltage divided by two: (170v/2) : 85v when working with 120v AC mains.

After getting the true 1/2 rectified RMS voltage after the diode I show how Ohms law is used to calculate the light bulb wattage needed to give the mystery resistance which gives us our final 12v and 150mA to the cooling fan.

V=IR
Where “V” is the voltage drop across the light bulb (85v – 12v) = 73V
“I” is the current through the circuit ~0.150A and “R” is the resistor we need to calculate.

73v = 0.15 * R
R = 73v/0.15
R = 487ohms

We can’t use any 487ohm restore because the current through it will be 0.15A and that could get real hot!

P=IV
P=0.15A * 73V
P = 11 watts

Most small resistors are only rated at 1/4 to 1/2 watts.  You can buy some high wattage resistors but then you’re not using scrap.

But I happen to know that 487ohms is real close to some incandescent light bulbs when powered off 120v AC.  And there will be no issue with a light bulb taking 11 watts.

To calculate the resistance of some light bulbs just run their ratings through the same equations as above.
Let’s do 100W, 60W, 40W and 25W bulbs.

100W bulb:
P=IV
100W = I * 120V
Solve for I:
I = 100W/120v
I = 0.833A

Now lets find its resistance when driven at this normal 120v AC.
V=IR
120v = 0.833A * R
Solve for R
R = 120v/0.833A
R = 120ohms
If we needed a 120ohm resistor running close to 120v AC mains power we can use a 100W light bulb

Now let’s do the 60W bulb:
P=IV
60W = I * 120v
I = 60W / 120v = 0.5A

V=IR
120v = 0.5A * R
R = 120v/0.5A = 240ohms

Now 40W bulb, which I used in my circuit:
P=IV
40W = I * 120v
I = 40W / 120v = 0.333A

V=IR
120v = 0.333A * R
R = 120v/0.333A = 360ohms

Just for completeness 25W bulb:
P=IV
25W = I * 120v
I = 25W / 120v = 0.208A

V=IR
120v = 0.208A * R
R = 120v/0.208A = 577ohms

A 25W bulb would have also worked for me but being it was getting higher than my calculated 487ohms I would rather use the lower resistance bulb.  I would rather my fan turn a bit faster than too slow to cool my motor.

Another thing to consider is that I’m not going to be powering my light bulb with 120v AC.  My light bulb is after my diode so it will be running on 85v DC such that it is only really on and conducting current 1/2 the time.  This will change the heating and the resistance of the light bulb but not enough to cause problems with my back of the envelope style of calculations for powering a fan.

So there you have it.  Three scrap components and you have yourself a hacked together 12v DC power supply.

Below is an oscilloscope screen shot of my final power supply signal across the fan. Notice the 3.4v peek to peek ripple riding at the 16v DC offset. That comes out to a 1.02v RMS ripple as the capacitor charges and discharges.  Not at all a good power source for some electronics, but just fine for my quick weekend hack.

This circuit could be used for any project that is not affected by the 1v RMS ripple but like I said in the video “This is just a quick weekend hack and should not be ran continues or unattended”.  Things could go real bad at anytime with such a circuit and you want to be there to shut it off. This is not a safe power supply circuit and should be used with extra care. I did not use a fuse and it does expose the user to dangerously high voltage if something should go wrong. This is a hack and should only be done by somebody who knows what they are working with and can do so safely. There, you have been warned.

If you watch the full video you will see that I replaced this hacked power supply with a more stable and safe alternative in the end but the hack did get me by for the weekend and I thought it would be an interesting hack to share.

If your needs are for more or less than 150mA then you can just rework the above equations to get the light bulb size you need.  Remember you can put light bulbs in series to get more ohms or parallel to get combined lower ohms just like normal resistors.  Also remember to pick a diode that can handle your target current and being this is just ballpark calculations you want to take measurements at your load to validate your power conditioning is acceptable.  I calculated for 12v but got 16.5v with a 3.4v p-p ripple which does work for a silly fan power supply but maybe not your project.

Thanks for following along and remember to subscribe to my YouTube Channel “toddrharrison” and my blog RSS feed.

The failure comes under the category of “Design Failure”.  Product designers not knowing the manufacturing tolerances and component tolerances they are working with.  In the case of these wireless classroom participation voting remotes the failure is with the batteries not making good contact.

Below is a photo showing how the thick plastic is preventing the battery’s positive tip from reaching the contact.  For some batteries this is not a problem, for others you get intermittent on and off events and for Duracell you get zip.

CLICK TO READ ALL —>:

This goes to show how important it is for designers to really know the manufacturing tolerance of the plastic mold injection processes they use as well as the minimum manufacturing height of AA battery tips.  So to fix this we just need to remove some plastic.

Below are just some photos of my repair so others can save their iClicker or any other device with similar intermittent battery contact failure. You have to take three screws out but one is under the sticker.

Below is the bit we have to cut out or shave down some.

Remove the positive battery clip.

Cut out some plastic with a sharp knife.

Once you get some BUT NOT ALL the platic cut out it should look like the below photo. If you cut out too much plastic your positive terminal clip will not stay in place.

Your clip should slide back in and still be held in place by the platic you didn’t cut out.

In the below photo you can see the battery now makes good contact and all batteries should work just fine.

There, the iClicker is working.  I know there is a lot of these remotes out there with this problem so don’t bring them to me, fix them yourself

I hope this was helpful.

Today I continue my rainy day power supply repair project. I have checked everything twice and even took a shot in the dark by replacing all the ICs on the board. I still don’t know why this circuit is not working. The power transistors on this board should supply a ground path for the motor when activated by a plus on their gates. The pulse is not appearing at the gates so I know at the heart of the problem the pulse width modulation chip (PWM) is not doing its job. I have replaced the PWM chip but that didn’t help.

In this video I dig a bit deeper using my oscilloscope to look at some select voltage signals going and coming from the PWM chip. I even bypass the PWM and inject a pulse train from my function generator to test the power conditioning and power transistors. I can’t simply replace the existing PWM chip with another manual controlled PWM chip because it currently uses current sense feedback as well as signals from adjacent control circuitry to not only start the plus train but also control its duty cycle. These are critical features for a treadmill or metal lathe motor control circuit in order to maintain a selected motor speed under load.

You may want to first read (part 1 of 7) of this blog post series.

I was going to post the next 5 parts separately but decided to just combine parts 2 through 6 in this posting. Below is the list and you can scroll to see each section. There maybe a final separate 7th posting on creating a “Corrective Raiser image Board” (CRiB) board to correct a slight design flaw with Adafruit’s SpokePOV boards as noted in part 6 below.

Part 2: Mounting an adjustable magnet on the bike frame
Part 3: Building bench testing rig for SpokePOV
Part 4: Programming images and setting the SpokePOV board offsets
Part 5: Halloween image and video of SpokePOV in action
Part 6: Troubleshooting an image skew problem

Part 2: Mounting an adjustable magnet on the bike frame

The SpokePOV kit comes with a very strong magnet which is used to trigger the Hall Effect sensor on the board as the board rotates with the wheel. In the suggested configuration from Adafruit the magnet just sticks to the inside of the bike’s front fork. This is not optimal because the magnet will not be adjustable with respect to the board and the magnet could easily fall off or move when encountering a bump. You could epoxy the magnet to the frame at a selected height but then the tire could be difficult to remove.

CLICK TO READ ALL —>:

My solution was to drill a hole in the front fork brake caliber, epoxy a nut over the hole and then epoxy the magnet to the head of a bolt. I then cut the bolt to an exact length so that when it is screwed in with a locking washer under a makeshift handle it would tighten up just hovering over the Hall Effect sensor on the POV board. With this rig I can easily back off the magnet when I need to remove the tire and I would never lose my magnet or alignment. What follows in this section are photos of this magnet mount mod.

Supplies: J-B weld epoxy 4 minute bond, Thin bolt, two nuts and one locking washer.

Grind the head of the bolt flat if it is not already flat.

Epoxy the magnet to the head of the bolt.

Drill a hole for the bolt through the brake caliber or other suitable part of the frame directly over the Hall Effect sensor on the POV board.

Put the nut over the hole on the inside of the fork. Use the bolt to keep it centered while you epoxy the nut in place.

Use a wire or wire tie to keep the bolt in place while the epoxy dries.

Put the 4 minute JB weld epoxy mix carefully around the nut. Don’t get any epoxy on the bolt or the inside of the nut. I used a tooth pick to carefully apply the epoxy.

Once the 4 minute epoxy is dry you can tighten up the bolt with a 2nd nut and lock washer so that the magnet is just over the Hall Effect sensor by about a 1/4 inch or less. I created a makeshift handle out of an old handle and some additional nuts and lock washers. I wanted a handle so I didn’t need to get out tools to get the tire on and off being the magnet would otherwise be in the way.

In this last photo you can see just how close I can set the magnet to the sensor on the POV board. This is best for getting a good clean Hall Effect trigger as the tire spins.

Part 3: Building bench testing rig for SpokePOV

I wanted a simple test rig for my font tire when programming and testing new images. I absolutely hated having the bike upside down with the tire on it when trying to program and test. If the bike tipped over it would yank my programmer and maybe even my laptop to the floor. Plus the images would always be upside down.

So I welded up this contraption in which I can quickly mount my tire and it securely clamps in my bench vise. The tricky part was adding the magnet to an extension rod welded to the test rig hub mount. It had to be welded at the same angle as my bicycle’s front fork with respect to the ground. You could build this out of wood just as easily but I have a welder so this was easy-peasy-lemon-squeezy for me. Here are some photos but you may want to also checkout my latest test rig that uses an old ceiling fan motor for the test rig.

There are some notes in the photos if that helps.

This is what I use to spin the tire. It is an old wagon wheel with the metal axel cut off.  I epoxyed the wheel to the axel so that the drill could spin them both as one.

Set the drill on high speed and this gets the wheel going quite fast.  Once again you may want to checkout my new ceiling fan motor test rig.

Part 4: Programming images and setting the SpokePOV board offsets

When I purchased my SpokePOV kit from Adafruit I also purchased their SpokePOV programmer kit. Really this I just their standard USBTiny ISP programmer with a named driver to make it simple for people that only use it to program a SpokePOV board. Turns out this is a very nice in-circuit programmer for programming many Atmega AVRs (click to see my posting on just such a project).

You do have to assemble your programmer kit but that’s what teenage daughters are for. Ha. This photo was taken during the assembly of the SpokePOV programmer.

The next step was to download and install the driver for your SpokePOV programmer and download the C++ software for image editing and programming. I recommend starting with a simple forward pointing arrow as your first image. You do have to connect the programmer to each board one at a time and load the same arrow image into each of the 4 banks on each board.

Make sure your programmer’s jumper is set to NOT provide power to the board, being the board should be self powered by batteries.

If you didn’t connect all three boards to the same Hall Effect sensor you are good to go, but if you want cleaner animation you should have connected the boards as I documented in part 1. With the boards linked all fire at the same time but each board is at a different location when they fire. This means that each board has to be programmed with a different image offset so all images overlay at the same exact location giving a super clean image at even low speed and with animation.

If your first image was a forward pointing arrow then setting the offset is simple. Label each board 1, 2 and 3 with a Sharpe. Start with only board 1 turned on and spin the wheel up to speed. Note the direction the arrow is pointing and calculate the offset needed to get the arrow to point forward. Stop the wheel, program this offset into board 1 and repeat until you get the arrow level and pointing forward.

PLEASE NOTE: in my photos there is a strange short vertical line perpendicular to my arrow. This is not intentional and seems to be related to a programming anomaly when writing the image to the boards memory banks. Sometimes this can be corrected by loading the image back from the board, erasing the erroneous pixels and re-uploading the image back to all 4 memory banks. This does not always fix this anomaly so I just live with it most of the time. (sad).

Next turn on both boards 1 and 2. When you spin up the wheel the 2nd board’s arrow image will be pointing in the wrong direction but board 1 will remain correct.

Once again calculate the offset needed to get board 2’s arrow to point forward. Stop the wheel, program board 2 with its new offset and repeat until both board 1’s image and board 2’s image are exactly lined up.

Repeat this process again for the 3rd board or as many remaining boards as you installed. The more boards you have the better your images and animations will be at low speeds. Write the offset on each board so you don’t have to repeat this process if the chip’s offset somehow get reset.

Part 5: Halloween image and video of SpokePOV in action

This is my daughter’s bike and she likes to program in an image for each season. Here she put up a pumpkin image she downloaded. (sorry I lost the link ). She has also done Christmas trees and so on and so forth. Lots of fun and a bit of added safety when riding at night.

Sorry but my camera does not do a very good job of recording. The images do look a ton better live.

Part 6: Troubleshooting an image skew problem

We noticed a perplexing issue with our images. The left side of the wheel, from the passengers view point, had a skewed image. The image forward of the hub was high by about 1.5 inches while the image behind the hub’s center point was low by 1.5 inches. However the image on the right side of the wheel looked just fine. This became very apparent if you wanted to display an arrow passing through the center of the hub on the left side or any other image passing through the hub.

This is a smiling face with winking animated eye on the right side which always looks good:

This is the left side that is always skewed.  Notice how the smile is high on one side and low in the other:

It actually turns out to be a mounting geometry issue which is unavoidable because of the layout of the LED’s on the board. The old “round peg in a square hole” issue. It took me one of those “I should have had a V8” moments to finally grasp what was going wrong. What follows is my troubleshooting approach and detailed conclusions and solutions.

Troubleshooting steps, detailed conclusions and solutions

I started my troubleshooting by turning on just one POV board but I had the same problem as I did with all three boards sharing a single sensor. I reinstalled the sensors on all three boards and each board had the same problem independent of the other boards.

I was convinced it was firmware so I downloaded the “C++” source code from Adafruit and started going through that but nothing jumped out at me as being a code issue between how the left and right side of the wheel was controlled.

I started examining the circuit schematic. It appeared to me that the latch select lines between the left and right side of the wheel maybe shorted or somehow crossed causing them to fire as if they were one side. I took out the micro controller chip and started tracing the 12 pins on all latch chips. But my digital multi meter said the two sides were not crossed physically so that wasn’t the problem.

Some brute force troubleshooting was in order. I pulled out the micro controller again and bent out pin 9 (“The left side select pin” on schematic) and re-inserted the chip.

Without pin 9 connected nothing was controlling the left side of the wheel so it was dark and as expected only the right side was on and the image looked good. I then repeated this test but this time I removed pin 8 (“The right side select pin” on schematic) and reconnected pin 9.

Now only the left side had lights on and the image was skewed as before with half the image high and the other half low.

I next bent out both pins 8 and 9 on the micro controller but I also crossed pin 9 to the connection point on the PCB where pin 8 would normally be connected. See the small U shapped jumper wire solderd in this photo near the spoke on the PCB.

At this point I would have expected only the right side to have lights and for the image to be skewed as it was when this pin controlled the left side. But that didn’t happen. The image was on the right true enough but the image looked just fine, not skewed at all. How could this be? If the problem was a firmware issue or other timing issue then pin 9 controlling pin 8’s side should have the same problem but it didn’t. The problem just seemed to evaporate.

I sat for a while just looking at the wheel and how the boards were mounted and then eureka! The problem now made complete sense. The board is square and the wheel is round! That can’t work because only one row of lights on one side can be pointing at the center of the hub which means the other side will always be skewed as it is drawing thinking the center of the wheel is in a different location than it really is.

I had mounted the boards flat on just one side of the wheel along one of the spokes. The boards are square and the lights on one side are aligned along the spoke therefore only one row of lights on one side can be pointed at the center hub.

Below is a photo of the good side where the LEDs line up almost perfect with the hub.
I drew in red lines to extend the line of LEDs through the center hub.

Below is a photo of the bad side where the offset of LEDs on the back side of the board are skewed off to the side of the center hub. Once again I drew in red lines to extend the line of LEDs skewed to the side of the hub.

This install method forces the lights on one side of the board to be pointed radial at the center hub leaving the other side’s row of lights skewed and NOT pointing at the center of the hub. I zip tied one edge of the PCB along one spoke and since my bike has a very small center hub ring for the spokes to connect to the problem was exaggerated over other bikes that have a larger center hub spoke ring.

This is an unavoidable side effect of the board layout and at best you can mount the boards NOT following a spoke and splitting the difference so that each side is slightly skewed but not as dramatically as it would be if you centered just one side of lights with the hub as I did. I guess one could also put the boards in the center of the spokes between the left and right side of the wheel and put a twist in the bottom of the board closest to the hub helping each row of lights on each side point a bit closer to the center of the hub but what a fuss.

A triangle shaped PCB board may have been a better design choice and would have allowed the LEDs on both sides to fall along a true radial line with the hub. Maybe this is a good idea for v2.0 perhaps.

I’m not sure this alignment issue can be corrected in the software or not. It would be more of a Hubble Telescope corrective surgery then anything else. Maybe the user could be instructed to measure the offset between the hub and the row of LEDs on each side of the board allowing the software to introduce some corrective timing. If anybody wants to tackle this corrective surgery of the firmware I’m sure all users of this board version would be greatly appreciative! Drop me a line if this ever comes to fruition.

For now my solution to this problem is going to be a pricy one. I plan on just cutting the 9 pin on each micro controller for all three boards so the LEDs on the left inside are off. Then I will get another 3 boards for the other side cutting the 8 pins or just not soldering on the right side components. I will wire all 6 boards to a single sensor, have the outward facing LEDs 100% inline with the center hub and each board will have its own rotational offset. This will create perfect animation on either side at all speeds.

Wait! I have a cheaper solution then buying 3 more boards but it will take some design time first. I could create a raiser board that bolts to the current SpokePOV board inline with the right side LEDs but on the opposite side of the board. I can then move all the left side LEDs to this new raiser board. Then both sides will have a line of LEDs 100% inline with the center hub.

I may have to design the board so the 4 latches also move to the raiser just to keep the wiring between the two boards at a minimum.

When I’m done with the raiser board design I will post the files alone with SpokePOV board modifications, wiring and mounting instructions. Others can then etch and mount their own “Corrective Raiser image Board” (I think I will call it the CRiB board).

1. What I bought for my tech bench.
2. Some models and prices of isolation transformers.
3. How to alter a public version into a tech version.
4. Helpful tips on using your oscilloscope safely with and without an isolation transformer.
5. How to be a little safer when working with high voltage live mains

These would be good tech isolation transformers that don’t need to be modified:
4.30A isolation transformer, 115/115VAC, 500VA
2.50A isolation transformer, 120VAC/120VAC, 300VA
1.25A isolation transformer, BK Precision BK1604A
0.43A isolation transformer, 115VAC, 50VA