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Tracker Cluster controller.

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rossw:
Haven't had so much time to work on this, but little bit at a time, half an hour here and there.

Software is just about ready to make its debut. PWM soft-start works great. Software-controlled current limit stops the thing pushing hard enough to damage anything if it gets caught or an actuator sticks. "Virtual Limit Switches" stop it driving past the angles I set etc. Send commands, query status, array angles, actuator drive current etc all working great.

Got a case that may have been made for the board. Bulkhead mounting, so it can just attach directly to the back of the tracker frame.
Here it is without the lid on:


And from where you'd normally "see" it when its mounted. I'll take another pic when installed.

Wolvenar:
Are you going to do your balloon trick with this one when it's ready for use?
Or is it not possible to seal up that well?

rossw:

--- Quote from: Wolvenar on March 27, 2013, 02:03:23 pm ---Are you going to do your balloon trick with this one when it's ready for use?
Or is it not possible to seal up that well?

--- End quote ---

This ones case is not waterproof - it's a "close fit" and water won't run into it, but because of that the balloon won't work.
Upside, because it's designed to mount UNDER the panels, it won't get much exposure to the weather (unlike a bright-spot tracker which has to directly "see" the sky)

I'll drill a small bleed hole and force some cotton thread in it to permit moisture extraction, if it becomes a problem I'll replace it with a waterproof case and do the balloon trick, for sure.

bj:
  Sure is nice and tidy Ross.  Doubt that water will be a problem, where you are mounting.
  Of course I've been wrong many, many, times before. :)

rossw:

--- Quote from: bj on March 28, 2013, 05:53:16 am ---  Sure is nice and tidy Ross.  Doubt that water will be a problem, where you are mounting.
  Of course I've been wrong many, many, times before. :)

--- End quote ---

Yeah, "plan for the worst, hope for the best" is a good policy though.

Have had a change in thoughts on recording the actuator current. Original plan was to just keep in in RAM and come back later to read it. However there are some technical issues with that - if anything happens on the bus, there's no way to recover lost data. So since the processor already has 256 bytes of  EEPROM internally, and I'm only using a dozen bytes for configuration information (device ID, calibration points for the 3-axis accelerometer, current limit, virtual limit switches, etc) - so I decided to store the actuator current in memory.

A quick calculation however, showed that if I stored a value every 5 minutes, for 12 hours a day - I'd "burn up" an EEPROM in 2 years (based on the manufacturers 'minimum life' figures). Of course, it might last much longer than that, but thats all I could count on. And frankly - designing something to fail in a mere 2 years wasn't good enough.

After some research, the cycle life is per cell, not for the entire EEPROM. So I've written some wear-levelling code that cycles over 100 bytes. It's a little bit tricky, but it takes the "designed failure" to a minimum of around 100 years if used every 5 minutes, 12 hours a day, every day. I'm happy with that!

Just a couple of tricky last bits to add, and I'm ready to put it in the field and try it!

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