How to build a 21st century protection board

Schematic - version 3.3

Jeff has got issues with attachments - trying to attach from my account.
Split in 5 pages.

Cheers,
Valery
 

Attachments

  • 01-Control-Board-3.3.jpg
    01-Control-Board-3.3.jpg
    258.1 KB · Views: 376
  • 02-Control-Board-3.3.jpg
    02-Control-Board-3.3.jpg
    197.4 KB · Views: 368
  • 03-Control-Board-3.3.jpg
    03-Control-Board-3.3.jpg
    269.6 KB · Views: 360
  • 04-Control-Board-3.3.jpg
    04-Control-Board-3.3.jpg
    274.6 KB · Views: 351
  • 05-Control-Board-3.3.jpg
    05-Control-Board-3.3.jpg
    229.4 KB · Views: 340
I added a couple extra outputs for future use as well. I didn't connect any of the analogue inputs though.

I'm more interested in this than the amps themselves. :rolleyes:

You don't know the massive "22 century" leap you would make with the thermal/
overload monitored by using the analog. Rails ... too .
Here , you could script the "trip" points .... allowing for individual amp customizations.

The Solar power people not only use these analog inputs , but tie a SD card
to the ATmega to log long term analog fluctuations (with time stamp).

OS
 
Yes, using analog inputs for monitoring / measuring certain parameters, will be the next "leap". Built-in ADC allows doing it quickly and afficiently, enhancilg capabilities to infinity :) Imagination is the limit :)

Thanks to Jeff for " tearing Arduino to pieces", so now we can use ATMega chip separately, making the board smaller and cheaper :up:

P.S. I have also recently developed a solution, utilizing 74HC595N shift registers, allowing increasing the number of digital outputs to as many as required (8 additional outs per register).

Cheers,
Valery
 
I thought about it as well. As far as the firmware is reasonably simple, it's ok to have it doing everything. But if we go for some relatively continuous analog tracking / processing, it's a good idea to have one chip mostly for startup/shutdown main cycle, and the other one doing all the rest continuous stuff independently, allowing protection to do its job very fast. ATMega chips are cheap ;)
 
I'm still kicking around the idea of datalogging. A Raspberry Pi might be a good option because of the ease of networking. I have no idea of coding requirements though. That's something I've never had the time to learn.

Ah, right - a good task for a separate board with network interface. Then, we can arrange a portal and collect the logs there. If something goes wrong, it will be easy to analyse the historical log and see the issues caused the problem :cool:
 
Do you think it would be safe to use analogue inputs to measure output device current? It would save quite a bit of external circuitry but the optoisolators are nice insurance. I would like to see thermal sensing done by the Atmega chip. It makes adjustment of parameters much simpler.

Yes, I think some simple, relatively linear opto-decoupling circuit will be more than enough. It can also perform some "integration" (RC), so that you measure not the raw audio signal, but somewhat averaged values.
 
For a very good linearity - yes, op-amps are required. But for our purpose - some simpler circuits may be tried...
A good example of a linear device - HCNR200 and HCNR201 (High-Linearity Analog Optocouplers). In the worst case, LM393 may be used for "normalizing" the receiving side of it (2 op-amps per chip).
 
Why not just monitor the power supply directly to detect an overload condition ?

OS

That's another option. It could become a little more involved with the supply being shared with multiple channels. Positive rails and negative rails would likely need to be monitored separately. Emitter resistors are a convenient source for sensing with no added hardware to the amplifier other than two wire connections.
 
Hi Andrew, in fact, overload and short-circuit protection for the amp is already implemented in existing design. We are now thinking about monitoring the rails and some other parameters in time with appropriate logging ;)

Jeff, the opto-couplers are linear enough, so even if we use op-amps for "normalization", it will only be required on receiving side. I mean - no isolated PSU required in any case.

Cheers,
Valery
 
So far the Mosfet relays look good. I need to crank some high current through them yet to check resistance. My Fluke 88 says Zero on low resistance setting with no load. Hopefully they run cool enough that I can lop the top off the boards.
 

Attachments

  • 2015-01-21 16.25.26.jpg
    2015-01-21 16.25.26.jpg
    654.8 KB · Views: 281
  • 2015-01-21 16.25.16.jpg
    2015-01-21 16.25.16.jpg
    832.9 KB · Views: 279