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#1 |
diyAudio Member
Join Date: Jan 2010
Location: Moscow, Russia
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Hi All,
Here is my development on microcontroller-based "smart" soft-start / protection, or, I would say, amplifier control board (see attached). Let's use this thread for discussions on firmware-driven boards - no matter what the PIC is, I believe, exchanging experiences will be useful for everyone interested. Cheers, Valery P.S. My firmware and gerbers are available on request ![]()
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If you can't explain it simply, you don't understand it well enough (c) Albert Einstein http://vzaudio.com/ Last edited by vzaichenko; 18th September 2016 at 05:49 AM. |
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#2 |
diyAudio Member
Join Date: Nov 2007
Location: near the House of the Mouse
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Shucks you are turning me back into a programmer analyst, writing code and developing hardware AGAIN
![]() But I am use to being that again, I want to focus on temperature and bias right at the output transistors, maybe mounting a LM35 right on the emitter or source pin right up next to the case, to read it temperature wise. While measuring the voltage drop across the emitter resistance, comparing them from device to device.
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Thanks ![]() Never give a Systems Analyst a screwdriver or hammer ![]() |
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#3 | |
diyAudio Member
Join Date: Jan 2010
Location: Moscow, Russia
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Quote:
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If you can't explain it simply, you don't understand it well enough (c) Albert Einstein http://vzaudio.com/ |
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#4 |
diyAudio Member
Join Date: May 2008
Location: Smoky Mountains , Tennessee
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I am deeply interested in this project - did you start with the "kit" on the
Arduino website ? As far as the active biasing , I'm sure it would work ... "map an analog in , use a pwm output to brighten/dim a led". (this would be another heavily filtered opto-coupler). But , what would happen in the case of failure ? Thermal runaway ! The advantages could be sensing a thermaltrack diode or collector pin SMD to update the micro in almost real time - still , analog backup would be nice. ![]() OS
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Wanderer - GREENAMP , less is MORE. https://www.diyaudio.com/forums/soli...ss-output.html |
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#5 |
diyAudio Member
Join Date: Nov 2007
Location: near the House of the Mouse
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What if we put together a demo board with one or two pair on it, a hundred watter or smaller to give everyone a chance to see how all this works. we could include a small prototyping area on the board to make things easy to add or changed. Maybe develop a schematic that could be easily bread boarded and shared, with lots of photos and code example. Kinda like the very good LTSpice thread that Molly has blessed the forum with. Lets start somewhere and let everyone find out that it is NOT hard to do at all, once you get past the basics. There are ton of UTUBE videos out there like I posted.
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Thanks ![]() Never give a Systems Analyst a screwdriver or hammer ![]() |
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#6 |
diyAudio Member
Join Date: May 2008
Location: Smoky Mountains , Tennessee
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Arduino = 16mhz clock - fast enough for basic bias adjustment. Also fast enough
for "on the fly" class A biasing with thermal feedback (safety). I don't know if it could handle absolute real time class AB2 "fancy" biasing or error correction. At this level , we would lose "analog" character .... better off with class D. It is not a PC , only 32K for any programming - (simple A/D -/set limits - then do X type operation). ![]() OS
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Wanderer - GREENAMP , less is MORE. https://www.diyaudio.com/forums/soli...ss-output.html |
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#7 | |
diyAudio Member
Join Date: Jan 2010
Location: Moscow, Russia
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Quote:
Big advantage of such controllers - they are real time. Meaning - no operating system. The only thing running - is your program. I don't like using PWM for such applications in audio - requires - as you say - heavy filtering and not reliable enough. I prefer using a hardware DAC, either having it as part of the PIC chip (there are some), or having it as a separate chip. As an option - there is an appropriate Arduino extension board. BTW, in some cases you may need more input/output pins, than Arduino can handle. In this case I use 74HC595N registers for extension and having the "locking" capability at the same time. They may be cascaded to have as much pins as you need (add up by 8 portions). So, you push the desired "number" to the registers and lock it there. Then, before it's time to change the "number", you can do whatever you want in your program - handle protection, indication, etc. I used this approach in one of my professional designs, having one register to extend the inputs and two - to extend the outputs. 32K is A LOT. In the beginning of 80-th (last century ![]() ![]() ![]() Arduino is lightning fast, comparing to that one ![]() P.S. I'm wrong - memory error ![]()
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If you can't explain it simply, you don't understand it well enough (c) Albert Einstein http://vzaudio.com/ Last edited by vzaichenko; 4th November 2014 at 09:19 AM. |
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#8 |
diyAudio Member
Join Date: Jan 2010
Location: Moscow, Russia
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Just had a power blackout in the whole building for 5 seconds.
AC power failure sensor triggered on the board, it disconnected the speakers immediately, then shut down the amplifier. PSU capacitors did not discharge in 5 seconds, so the board stayed alive, indicating "AC Failure" - one short flash every 2 seconds (Power LED). Just as expected ![]()
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If you can't explain it simply, you don't understand it well enough (c) Albert Einstein http://vzaudio.com/ |
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#9 |
diyAudio Member
Join Date: Jun 2014
Location: New Hamburg, Ontario
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I'm playing with a slewmonster right now and am having some weird DC offset issues on startup. My protection seems to trip around 2 volts. Is that around the threshold it's supposed to happen at? This is kind of a good test for your circuit.
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#10 |
diyAudio Member
Join Date: Jan 2010
Location: Moscow, Russia
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Yes, this is around the threshold. Does it trigger?
Ah, ok - it does ![]() Yes, I had it shutting down the amp a number of times as well during some dangerous experiments ![]()
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If you can't explain it simply, you don't understand it well enough (c) Albert Einstein http://vzaudio.com/ Last edited by vzaichenko; 5th November 2014 at 11:02 PM. |
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