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Category: electronics

Garmin’s Incomplete Edge 305 Fix

Published August 27, 2010

As you may have noticed by now I occasionally fix Garmin Edge 305 cycling GPSs that have a known problem where they will suddenly power off during use. This is caused by the spring contacts for the battery bouncing free from the battery contact and the device momentarily losing power, leaving it in an off state. To remedy this I move the battery wires from the contact PCB directly to test pads on the main board, completely bypassing the iffy spring contacts.

It appears that Garmin is aware of this issue and has tried to remedy it in recent versions of the Edge 305. Tonight when I pulled apart another one apart I found foam rubber stuck under the contacts apparently to provide additional pressure and avoid the problem. Clearly this did not work as otherwise I would not have been repairing this one. I can only hope that Garmin has a much better design in the Edge 500 (and future models) to completely avoid this issue.

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Edge 305: Crashed Hard

Published August 2, 2010

I’m working on a Garmin Edge 305 for a friend’s boss which was reported to have a problem finding satellites. After reproducing the problem I opened it up, only to find the body of one of the tactile switches missing and apparently nowhere to be found. This was quite a mystery, as the case had supposedly never been opened before.

After opening and closing the case the not-finding-satellites problem appeared remedied (likely by the full power cycle), but I was confused by the apparently missing button. Rob’s boss had reported that the missing button had been “acting up”, but with all these parts missing the button simply wouldn’t have worked. With the underside of the battery the only place the pieces could have possibly gone I popped out the battery only to find all three pieces stuck in the adhesive which normally holds the battery to the chassis. While they are the size of (large) grains of rice I was able to get the switch reassembled and functioning. Unfortunately, the not-finding-satellites problem is back.

This means that the owner had to have crashed hard enough to blow apart a tactile switch through the rubber housing, bounced it around enough to get all the pieces under the battery, then squished (squeezed?) it all back together. I suspect that in the process a (quite inaccessible) solder connection on the GPS module broke, the metal bits bouncing around the case shorted something out, or something else in the case broke leading to the issue of satellites not being found. It’s too bad I can’t fix that part.

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Another Edge 305

Published July 22, 2010

Today I fixed another Garmin Edge 305, although it’s still a bit strange. This one wouldn’t find any satellites, so I pulled it open to look for broken solder joints and after nothing seemed awry I tried it again and it worked fine. I suspect that it just needed some manner of hard power cycle to get it working again.

What’s also strange is that the down arrow button isn’t working, apparently due to the top and plunger of the tactile switch not being there. When I opened the device they weren’t there and I really can’t tell where they went, as the unit appeared sealed. I can’t help but think that it was dropped, the switch broke, and something happened which caused the GPS to need a hard power cycle. Despite this I couldn’t find the switch parts in the case, either by removing the PCB or tapping/shaking it to dislodge things under the glued in battery.

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Purple Foam Block

Published March 21, 2010

After getting the battery and power supply going the next step in the bicycle video recorder project was to fit everything in the case. The foam block seen above, carved out of a $2 remnant from The Foam Factory, is a big part of this, as it supports the recorder, battery, and power supply inside the bag. Everything is now assembled, and I’ve even gone for a quick test ride around the courtyard, as seen in this video.

Photos of today’s work begin with the blocks of foam here and end on page 6.

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Battery + Power Supply: Go

Published March 20, 2010

Today I received the voltage regulators to be used in the aforementioned power supply for the Bicycle Video Recorder that I’m working on. They fit perfectly in the PCB that I’d made, and worked exactly as expected. As the battery had a slight charge when received from All-Battery.com I was able to use it to test out the assembled power supply — as seen above — and I’m getting a proper 5V and 12V out of it. This is good.

Tomorrow I’ll give the battery a full charge, as I want to do the first charge in a relatively safe area, just in case something bad happens. I’m also hoping to finish up the routing and assembly of cables that will hold it all together. After this is done the setup should be ready to record video, and I should then be able to take it for a test ride and get on with battery life tests.

Figuring out where to run all the wires (out which sides of what) and how to bundle it all up in the bag will be a bit of a challenge. I’ve got an assortment of foam to use for padding things, but I’m not yet sure how I’ll arrange it all. The SanDisk V-Mate needs open access on the top during use, and the battery has to remain easily removable / unpluggable after use.

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Power Supply for Bicycle Video Camera

Published March 6, 2010

I’ve been working on a video camera system for my bike. The project is just getting started, but today I made the PCB for the power supply. You can see it above fit inside of its project box (a RadioShack 3x2x1″), or you can see the bottom side with solder and traces here.

It’s been a few years since I last etched a PCB, and as I’d run out of photoresist developer (a lye solution) I decided to make due with what I had readily available and laid out the board by hand, drawing it in pencil and marker and using nail polish as resist. I’m quite happy with how it came out. The many-year-expired tin plating chemicals that I had sitting around the basement even worked, giving it a nice tarnish-resistant silver finish.

This PCB and housing is designed to hold two eBay special step-down DC to DC switching regulators (buck converters) to get 5 VDC and 12 VDC from a 14.8 V 3000mAh LiPo battery pack. The 5V will power a SanDisk V-Mate solid state video recorder and the 12V a VioSport Action Cam 3. All of this together with an 8GB microSD card should allow for the continuous filming of eight to nine hours of mobile video while fitting in a small bento-style bicycle bag.

Now to wait for the rest of the parts to arrive so I can put it all together. The camera and recorder are here, I’m just waiting on the hand grenade battery and charger, bento bag, regulators, and powerpole connectors. Hopefully this won’t be too bad for a ~$200 project. The video quality should be decent as shown by this intentionally shaky test which features Danielle and Roxie (warning: contains dog nose) and single-charge recording length should be long enough to capture any bike ride that I might choose to record. More photos are available here, if you’re interested.

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The Last SDrive NUXX

Published February 4, 2010

With this shipment the very last SDrive NUXX is sold, and the project is complete. The bare PCB on top is the first / prototype device with retrofitted ZIF socket. I may use it for future development work, or I might just keep it around as a memento.

Now, time to find another project.

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IS1621N on BCK-08 PCB

Published January 19, 2010

In other cheap Chinese device news here’s DealExtreme p/n 8422 with the case removed, powered by a benchtop supply, peered to my Nexus One, and playing audio. I’m hoping to redo the output circuitry on this and put it in another case to make a decent Bluetooth audio device for connecting to either a home or car stereo. It runs off of 3.7 VDC and has an on-PCB antenna, so it should be pretty easy to work with.

The PCB contains an I.S.S.C. IS1621N and FM24C08B EEPROM, which likely contains the IS1621N’s config. I’ve requested the data sheet for the chip from I.S.S.C., so hopefully I’ll have that soon and can work on it. I’d also like to change the identifier string in the EEPROM, but I probably won’t touch that until I know what the IS1621N expects to find in other parts of it. I also hope to find an example implementation, as it should be easy to build off of that to get line level output.

Here’s a few more pictures of the board:

· Detail of the FM24C08B EEPROM which likely houses the config for the IS1621N on the BCK-08.
· Top / button side of the BCK-08 PCB.
· Bottom / component side of the BCK-08 PCB showing the I.S.S.C. IS1621N Bluetooth IC and FM24C08B EEPROM.

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TFXTDOL

Published January 19, 2010

I guess this is what I get for buying discount ZIF sockets on eBay: one “genuine” TFXTDOL-brand DIP28 ZIF socket. It’ll probably be fine, even though I had to fight with pins which are too wide for sockets and almost too wide for the drill holes in one of the SDrive NUXX prototype boards.

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