Random Resets, Sync Issues, and IC Socket Stability

[jof]

I've been having some issues with some random resets and syncing my POVs together. So I wrote up some fixes on my blog with my other SpokePOV stuff. From http://thejof.com/blog:

So far, I’ve been quite happy with my SpokePOVs. They’ve worked fairly well together without any real signaling or coordination between them. But I have had a few problems, and I thought I’d write them up in case someone has similar problems. I’ve been having a lot of random resets, sync issues, and … uh … IC socket stability. Yeah, that’s what I’ll call it.

I’m suspecting a couple of reasons for the random resets. Since I like to really rip along on my bike about as fast as I can manage, centripetal force begins to cause some problems. In particular, I think that it’s causing the AA batteries to pull hard enough out that one or more comes out of contact with their battery clips and causes the microcontroller to do a hard reset. I’ve made a temporary fix by bending the clips in a little, but it’s still not perfect as they still band back after a day or two. I’ll probably either drill some holes at the tops of the tabs and tie the two tabs together, or place all of the batteries towards the hub of the tire and just use the external power connector on the boards. The other reason they might be resetting is the trace that gets cut on the board for three batteries (I’m using the higher voltage blue LEDs). I’ve noticed that flexing the boards can make two of them reset, and I suspect that I didn’t cut deep enough, and the foil of the trace just touches and comes apart from itself. But the more obvious indicator of this condition is that if I flex the board just right, the LEDs come on really dim, and my multimeter reads 3v on the power input.

Sometimes a random reset will cause my pattern of images to get confused from the others and causes a ghost of one image to come over the one displayed by the other two. I’ll fix this eventually by tying together one hall sensor to all three SpokePOVs and fiddling with the rotation offset in the firmware. Even if I do this, one could be out of sync from a reset (which I plan to fix anyway). To combat this, I’m actually thinking of tying a line to either another microcontroller, or between an adjacent POV that would have an interrupt that sends what rotation and frame it’s on so that other POVs could sync up to it. I haven’t bothered to write software or wire anything up yet though, it’s just an idea.

The last problem that I have is having ICs come out of their sockets, particularly my SPI EEPROM. If I get going fast enough, it actually begins to rock out of its socket a little. Luckily it hasn’t come all the way out yet. I’ll probably just epoxy it in one of these days.

[Olaf Marzocchi]

Maybe the layout should be redesigned, with an external board located near the the axis of rotation (hub).

[jof]

Maybe the layout should be redesigned, with an external board located near the the axis of rotation (hub).

With the purpose of?

I think that I'll eventually put all the heavy stuff (e.g. batteries) closer to the hub and carry the light stuff (electrons) with a wire to the controller and lights since the ratio of easy-to-implement to positive effect on resets is pretty low.

[adafruit]

I’m suspecting a couple of reasons for the random resets. Since I like to really rip along on my bike about as fast as I can manage, centripetal force begins to cause some problems. In particular, I think that it’s causing the AA batteries to pull hard enough out that one or more comes out of contact with their battery clips and causes the microcontroller to do a hard reset. I’ve made a temporary fix by bending the clips in a little, but it’s still not perfect as they still band back after a day or two. I’ll probably either drill some holes at the tops of the tabs and tie the two tabs together, or place all of the batteries towards the hub of the tire and just use the external power connector on the boards.

there are 4 mounting holes per battery so you can ziptie the batteries in.

The other reason they might be resetting is the trace that gets cut on the board for three batteries (I’m using the higher voltage blue LEDs). I’ve noticed that flexing the boards can make two of them reset, and I suspect that I didn’t cut deep enough, and the foil of the trace just touches and comes apart from itself. But the more obvious indicator of this condition is that if I flex the board just right, the LEDs come on really dim, and my multimeter reads 3v on the power input.

well thats easy to fix, just make the cut wider?

The last problem that I have is having ICs come out of their sockets, particularly my SPI EEPROM. If I get going fast enough, it actually begins to rock out of its socket a little. Luckily it hasn’t come all the way out yet. I’ll probably just epoxy it in one of these days.

[/quote]

superglue, etc. you can get machined sockets that might be more secure but really the amount of vibration you're putting on it is extremely rough for any scoket

[adafruit]

Maybe the layout should be redesigned, with an external board located near the the axis of rotation (hub).

you dont have to...there's also a way to attach an external battery pack (J1) so you can put batteries near the hub

[jof]

there are 4 mounting holes per battery so you can ziptie the batteries in.

I can't believe I didn't realize that's what those were for. Doh!

While the added hold against the board will probably make enough lateral friction to stop sliding entirely, the issue is the lateral motion of the batteries from centripetal forces.
It does mean using three or more zip ties per board every time I need to change batteries. The more permanent solution will be a generating hub or a separate, rechargeable, homebrew pack.

well thats easy to fix, just make the cut wider?

Yeah, I just did that tonight, and it seems to have been the source of the problem. A small jeweler's saw proved invaluable here.

superglue, etc. you can get machined sockets that might be more secure but really the amount of vibration you're putting on it is extremely rough for any scoket

This is true, and I've superglued the ICs in. Should no longer be a problem.

[matajumotors]

I had random resets, going into standby, hanging, not powering off etc. too. But i fixed it. At he start i thought it is because of my sensor (i do not use hall-effect sensor i use mechanical magnet sensor also self-made pcb's) but the problem was with power supply to ATTINY. I soldered near the ATTINY a 0,1uF capacitor an all problems gone!

[MadOverlord]

Could you post a picture of exactly what you did?

[matajumotors]

somethink like this:

[MadOverlord]

TYVM
R

[Unicyclist]

It does mean using three or more zip ties per board every time I need to change batteries. The more permanent solution will be a generating hub or a separate, rechargeable, homebrew pack.

I've got one word for you - Velcro - I sewed two pieces of eyeglass retainer straps to some Velcro and presto a re-usable battery retaining device. Although it was tough getting my sewing machine to go through the PC board <joke>! It was a little hard running the second piece of Velcro on the sewing machine, but I managed it - it would be easier before soldering the LEDs.

If you think a bike is tough on the batteries, you should try a unicycle!


For more great re-usable SpokePOV stuff see http://www.ladyada.net/forums/viewtopic.php?t=banned or how to mount a SpokePOV and still be able to remove it - without cutting any Tyraps.

[nyar]

Very nice!

[Unicyclist]

This is true, and I've superglued the ICs in. Should no longer be a problem.

One of the tricks I've used at work is to use a small bit of RTV - it can be cut but will hold the chip in place - if you're going to super-glue it, you might as well leave/take out the socket and solder the chip right in, because you will probably have to destroy the socket to get the chip out. Of course there are many types of RTV some with light hold and some that you'll need Hercules to pull apart, the light hold is good enough for this and can easily be cut. Be careful not get any in the socket holes, we usually put a daub on the ends of the chip and socket down to the board - if you've really got a problem, run stronger RTV from the ends and across the top.

[MadOverlord]

If you want stuff to stay in place, but want to be able to change your mind, then a hot glue gun is your best friend. I use it in my combat robots to both fix cables into sockets, and as insulation on terminals.

[Unicyclist]

If you want stuff to stay in place, but want to be able to change your mind, then a hot glue gun is your best friend. I use it in my combat robots to both fix cables into sockets, and as insulation on terminals.

Oh, I like it!