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How to build a 21st century protection board
How to build a 21st century protection board
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Old 6th November 2014, 03:25 AM   #21
benb is offline benb  United States
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Okay, now on topic. I recall a similar thread a few years ago regarding speaker protection rather than amplifier protection, and I posted my thoughts about it there:
microcontroller based protection system

My thoughts on amplifier protection are similar. If one measures the instantaneous voltage and current across each output transistor, one can calculate the instantaneous power being dissipated in it. This could be averaged over short periods of time (perhaps 1/10th second), and if that average is "too high," then the amplifier can be shut down before the output transistor's die temperature gets too high.

This would require sampling the voltage and current at above-audio rates (such as CD's 44.1ksps) and doing the appropriate calculations, which may exceed the capabilities of an Arduino's AVR processor. A 32-bit microcontroller such as an ARM (this is a licensed architecture, and many maufacturers make various versions of ARM microcontrollers) can do this easily.

One of the latest Arduino boards has an ARM chip in it, the Arduino Due:
Arduino - ArduinoBoardDue

In the last year or two I've been using some ST "Discovery" boards with ST's ARM chips on them. The programming is perhaps an order of magnitude harder than 8-bit microcontrollers because of the complex I/O that these chips have. There are perhaps a dozen registers just for the GPIO (whereas the original 8-bit peripheral chips had two registers for a GPIO port, the I/O register and the data direction register). I've got up to speed on most of this, but it's been time consuming. Using the Arduino Due for something like this seems like a fast way to utilize the power of an ARM chip.
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Old 6th November 2014, 03:40 AM   #22
jwilhelm is offline jwilhelm  Canada
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Would there be much more work to stepping up to a Beaglebone or Raspberry pi? I don't know anything about their coding but the GUI might be nice. Lots of processing power and on board ram.
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Old 6th November 2014, 03:49 AM   #23
tauro0221 is offline tauro0221  United States
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Hi,
I am using Zbasic and Basic MIcro and you can do any calculation using floating point with no problem. Both used the Atmel AVR ATmega328P. Same as the Arduino Uno. I do not know yet if Arduino have floating point since I just atarted to use it. Both are programmed in just simple basic language.
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Old 6th November 2014, 03:56 AM   #24
glen65 is offline glen65  United States
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Quote:
Originally Posted by vzaichenko View Post
Hi All,

Here is my development on PIC-controlled "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
Looks interesting, but one needs to ask if in the end this is really going to protect
speakers better than what's already being used. I would be concerned that the added
complexity could in itself create an issue.

I'll just let this guy say it..
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Old 6th November 2014, 04:11 AM   #25
tauro0221 is offline tauro0221  United States
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Hi,
The advantage of the micro it is that everything it is in the programming and it make it easy to do changes without need to change the hardware. Also it minimizes the components part counts.
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Old 6th November 2014, 06:56 AM   #26
vzaichenko is offline vzaichenko  Russian Federation
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How to build a 21st century protection board
Quote:
Originally Posted by benb View Post
First, let me get this off my chest:

It appears that "PIC" has become a genericized name that many people use for ANY microcontroller. This can make for a lot of confusion. It just did for me in this thread, until I saw what was happening.

"PIC" is a registered trademark for a specific line of microcontrollers made by Microchip:
Microchip Technology Inc
Microchip has been making PIC microcontrollers for decades, and I can see why people might use PIC as a general term for any microcontriller, but it's still not a generic name for a microcontroller. The PIC name should only be used for MICROCHIP's microcontrollers.

The Arduino (and "Arduino compatible") boards use AVR microcontrollers made by Atmel:
http://www.,atmel.com
Atmel's AVR microcontrollers are incompatible with PIC microcontrollers (even though they may have comparable features). If you call it anything other than a microcontroller, you should call the microcontroller on an Arduino an AVR.
Hi Benb,

Agree. Although, in some publications PIC is used as a general acronym, meaning Programmable Interface Controller / Peripheral Interface Controller. Well, pretty confusing
And of course, Atmel's ones are AVR.

Cheers,
Valery
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Old 6th November 2014, 07:25 AM   #27
vzaichenko is offline vzaichenko  Russian Federation
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How to build a 21st century protection board
Quote:
Originally Posted by glen65 View Post
Looks interesting, but one needs to ask if in the end this is really going to protect
speakers better than what's already being used. I would be concerned that the added
complexity could in itself create an issue.

I'll just let this guy say it..
That's What You Get For Missing Staff Meetings - YouTube
Hi Glen,

No, it's not about protecting the speakers better. It's about flexibility of control and status indication. Regardind added complexity.
1) Critical for speakers - DC offset protection - is a fully analog circuit on my board, very simple and straight-forward. It will work even if the microcontroller fails completely.
2) I often deal with the hybrid power amps involving vacuum tubes. In this case, soft-start sequence is more complex, than normal, if you want to do it right. You power-on tubes heating first. Indicate you're in soft-start sequence. Wait 20 seconds. Switch-on in-rush relay. Wait 3 seconds. Power-on completely. Wait 10 seconds. Check DC offset and over-current sensors. If OK - connect the speakers and indicate "Ready". If you imagine the same thing done by fully analog / fixed logic circuit - possible, but MUCH more complex. So, microcontroller management brings simplicity, not complexity. My first priorities, while designing the board, were flexibility and simplicity.

Cheers,
Valery
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Old 6th November 2014, 07:47 AM   #28
vzaichenko is offline vzaichenko  Russian Federation
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How to build a 21st century protection board
Quote:
Originally Posted by jwilhelm View Post
Would there be much more work to stepping up to a Beaglebone or Raspberry pi? I don't know anything about their coding but the GUI might be nice. Lots of processing power and on board ram.
Jeff, with Beaglebone or Raspberry pi you find yourself in a bit different environment.
Advantages: lots of processing power, lots of RAM, programming tools, etc.
Key disadvantage - those are not real time. You normally have an operating system there. Well, I have managed my program, running on Raspberry pi under Linux, working as almost-real-time...

Anyway, AVR chip is way more than enough for the purpose, if used properly.
Again, its main purposes are management and indication. As much, as you can imagine In this particular design, I used minimalistic approach, indicating all the statuses with a single LED
Someone may want to have those statuses written on the front-panel screen: "Sorry, I had to disconnect the speakers due to +2.5V DC offset in the left channel"
Or store all the telemetry in the cloud via internet uplink, so that you can see your alerts history and current status at the web portal wherever you are in the world. Also no problem

Cheers,
Valery
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Old 6th November 2014, 11:02 AM   #29
jwilhelm is offline jwilhelm  Canada
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Quote:
Originally Posted by vzaichenko View Post
Jeff, with Beaglebone or Raspberry pi you find yourself in a bit different environment.
Advantages: lots of processing power, lots of RAM, programming tools, etc.
Key disadvantage - those are not real time. You normally have an operating system there. Well, I have managed my program, running on Raspberry pi under Linux, working as almost-real-time...

Anyway, AVR chip is way more than enough for the purpose, if used properly.
Again, its main purposes are management and indication. As much, as you can imagine In this particular design, I used minimalistic approach, indicating all the statuses with a single LED
Someone may want to have those statuses written on the front-panel screen: "Sorry, I had to disconnect the speakers due to +2.5V DC offset in the left channel"
Or store all the telemetry in the cloud via internet uplink, so that you can see your alerts history and current status at the web portal wherever you are in the world. Also no problem

Cheers,
Valery
I can see it being an issue not running in real time. I'm looking at integrating a Beaglebone with Runeplayer into an amplifier for my office, that's what got me wondering. I've installed quite a few Sonos systems and like the interface, but not the sound.
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Old 6th November 2014, 05:03 PM   #30
Krisfr is offline Krisfr  United States
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The Due looks good, I am going to order one. Those dual DAC's look promising for Dynamic Intelligent Bias control with Artificial Intelligence. Sorry, I was dreaming out loud...

Just some thoughts...

Please tell me if we as a group could address the following areas individually and collectively as a whole for the "micro-controller". A gathering and sharing of individual solutions to each.

1. Voltage sensing
2. Current sensing
3. Bias sensing and control
4. AC power control for 110/220
5. Remote control
6. Opto Isolation of computer from amplifier
7. Speaker Protection
8. Display for testing and for final completed amps in the form of performance parameters

Then once we have these solutions, we could then apply them to a known good working amplifier and tested. Then have cut and paste solutions to apply to any amplifier under development.

Thanks to everyone that has commented and shared, great beginning!
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