Category: Electronics

Explorations in things electronic

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Resurrected power supply

A couple years ago, the power supply in my computer went belly up because the power switch had corroded and stopped being a switch.

Corroded power switch
Corroded power switch

No idea what caused it to become so badly corroded, but I finally got around to finding a new switch for it. The new switch fit perfectly into the opening, and getting it reconnected was a pretty simple job.

Now I’ve got a couple of power supplies to work with. Plenty of projects out on the web describing how to turn computer power supplies into useful bench power supplies, and I could definitely use a couple of those on the workbench.

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Hard drive motor as a rotary encoder

This is a pretty neat application. I guess I should have saved those motors from the hard drives I’ve dissected.

Found via Hackaday.

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Phantom volume

The TV started doing this strange thing where the volume would turn down all by itself. Even after turning the volume back up, it would go back down again all by itself. TV works fine after several hours of watching, but then the volume on-screen display (OSD) will pop up randomly and sometimes the volume will change. After a while, the volume OSD pops up with increasing frequency, and the volume drops more and more until eventually it’s doing it all the time.

Ruled out the remote sending out random signals to the TV. Even took the batteries out to guarantee the remote wasn’t doing anything.

The control buttons on the side of the TV are capacitive touch buttons, so I thought maybe those had gone screwy. Opened up  the TV and disconnected the control buttons, but it ended up having no effect. Still ended up with the same behaviour after a few hours of the TV being on.

TV innards
TV innards
TV power supply board
TV power supply board
TV control board
TV control board

At this point, I figure the problem is probably something heat related since the phantom volume changes don’t start happening until the TV’s been on a while. I’m not sure where else to go digging for the problem.

Looks like replacement control boards can be obtained from various sources for not a whole lot of money (definitely less than replacing the TV). Swapping out the control board would probably take care of the problem, unless of course the problem lies elsewhere.

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Garmin StreetPilot 2610 guts

On the dissection table today is an old Garmin StreetPilot 26100 GPS unit. This is one I used in the car about 7 years ago, and then has been sitting in the console box since I got cell phoned.

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Undoing about 5 screws was all it took to separate the two halves of the GPS unit. A couple of ribbon cables and a wire connected the two halves.

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Disconnecting the ribbon cables and wire gets us a good look at the boards. The board on the back half of the unit contains the CF card slot, mini-USB port and connections for power and computer connection.

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The front half of the board is where all the interesting stuff is. Co-ax cables go from the patch antenna (top) and auxiliary antenna connector to the ICs that handle the GPS bits under the metal cover. Ribbon cables connect to the display, rear circuit board and the buttons at the front.

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The patch antenna showed some discolouration and scratches. Not sure if that was during manufacturing, or if the unit was previously disassembled.

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The patch antenna is soldered directly to the board and to the metal shield, so if I’m going to re-use it for something, I’ll have to cut it off. Removing the cover from this part shows a 32.735 MHz crystal and a bunch of other unidentified components.

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Underneath the other shielding section on the right side of the board is the brains of the unit, a 16/32 bit ARM core RISC microprocessor.

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Removing a few screws separates the main board from the display module. The other side of the main board contains a few more large ICs underneath a shielded area (128 Mb SDRAM, 512 Mb flash RAM, 16 Mb flash memory, Garmin BIOS ROM) and components associated with the display module.

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Moving on to the display module, bending out a few tabs allows it to be removed from its metal frame. The touch screen display module consists of the front glass, the LCD module, some plastic gratings/diffuser sheets and the backlight unit. It’s an interesting little module. The backlight unit consists of a U-shaped light that shines into a block of plastic. One side of the plastic has a matted finish to help diffuse the light.

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On top of the light are some plastic diffuser sheets that polarize, scatter and block some of the light.

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Finally comes the LCD unit. Seems to be a pretty run of the mill LCD.

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Not a whole lot of re-usable components in here. I’ll clip off the patch antenna for the junk bin and keep the buttons and mini-USB module. I might try to remove some of the larger components off the boards. Aside from that, the rest of it will probably end up in the electronics recycle box eventually.

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Communicator panel

I’ve had one of these Star Trek door chime panels hanging up on the wall for quite a while now.

Star Trek communicator panel

It’s pretty cool, although rather limited. The button on the front plays the Star Trek communicator panel sound. When motion sensors on the side are triggered, the panel can play the door swooshing sound, a red alert klaxon sound or no sound (determined by the sliding switch on the front).

Over the weekend, the thought popped into my head that I should get a second one and modify it to also function as a wireless intercom system. Push the button, it plays the communicator panel sound and activates the intercom. Add a microphone behind the speaker grill and some LEDs to light up the white indicator box when the intercom is active. How cool would that be?

I’ve been pondering ways to do this. Cannibalizing an old intercom system or maybe even a couple of FRS radios should be a relatively easy turnkey solution. Something Arduino based using a Pro Mini or Pro Micro with some kind of low power FM transmitter might work too, but require considerably more effort to develop. I haven’t opened mine up so I don’t know how much room there is to cram stuff into.

I’ll let it spin around in my head for a while, maybe hit a couple of thrift stores to see if there’s anything interesting to work with. With the move coming up, it will probably be a while before I have much time to work on this.