[j4cbo]

I haven't built this yet, but I do have the basic design worked out...

- Monitoring done with Atmel ATtiny24 microcontroller
- Two differential input channels supporting any amplifier topology (2-channel, 3-channel, 4-channel differential, single- and dual-power-rail)
- Onboard +5 transformer and supply, for use with momentary power switches
- LED output; the micro can be programmed to flash during power-up and power-down, or when offset protection triggers
- Power rail monitoring for over/under-voltage cutoffs
- All analog stuff done with one TL084 quad op amp
- Charge pump inverter included for -5 power supply
- The TL084 power inputs are supplied with diodes, so it runs off of the larger of +/- 5 volts or your amplifier's power rails (won't run in to the +5 rail with an F1-type amp, for example)
- Two relay connections (for output and mains)
- RS232 for voltage/limit-setting, real-time monitoring, firmware updates, etc.

Here's the schematic.

Thoughts? Suggestions?

 

[MASantos]

THis looks like a looks nice. Let me see if I understand correctly:

1.THis will allow the use of momentary switches to control on/off funtion of the amplifier.

2. Will monitor the power supply voltage and if any value changes abnormaly, will cut power( or does it disconnect the headphone output?)

3. Will cut the headphone output if DC offset is exceeded(defined by user or fixd?)

Any other funtions I have missed? Could you incorporade a start delay funtion? Or is this already featured?

I don't see the relays in the schematic... where are they? Also, do you have a board designed done?

Can you estimate parts cost? Do you pretend to prototipe this? Sell boards in the future? It certainly looks interesting, please let us know more details.

Good luck with it!

Manuel

 

[flecom]

it would be nice if you had the option to make the power LED "throb" (a-la powerbook sleep) during a failure... thats what i did with some relay logic and amb's DC-offet boards...

i like the design a lot, but unfortunately most people dont have the means of writing the software/programming/burning microcontrollers

 

[j4cbo]

MASantos:

1. Correct.
2. I'd have it cut power completely, to prevent a bad power supply from damaging the amp boards themselves.
3. Correct.

The functionality would all be software-defined, and all programmable / user-selectable. A turn-on delay is possible, or it could simply turn on the outputs as soon as the voltages are within range (rather than adding a preset delay).

The parts cost about $35, including a 1.6VA Amveco transformer; if you already have ~7V always-on AC available then it's closer to $20. I do plan on prototyping it, although I'm going to be away from my work space until the beginning of January.

Relays aren't in the schematic; the idea is that you'd use your own relay close to the AC input and signal output connectors. rather than routing everything through this board. I'm working on a board layout.

flecom:

The microcontroller has PWM, so I could do brightness control and the classic throb/breathe pattern.

If all goes well and I do wind up selling boards, I'd include a pre-burned microcontroller chip with it.

 

[MASantos]

I didn't understand that this involved programing. That is way behind my scope. But if you preburned the IC than it would be much easier.

I will be away fromJanuary till August so I wouldn't be building it before next fall. But I would certainly be interested in one or two boards.

A few more questions:

What is in the signal path? Only the relay?

I can't see the relays in the schematic, where are them.

Manuel

ps: some parts of the schematic are cut in the atachment, can you upload a larger picture? thanks

 

[DaKi][er]

Love the design

If i were to do something similar of course I would do things a little different, as the only thing I don't overly like I the charge pump to generate the negative rail when there is already a transformer there to do it, as well as I'm not a PIC person and would either use an 8051 which I know inside out or take the opportunity to pick up an AVR

Otherwise it is all round a great design

 

[j4cbo]

Quote:

Originally Posted by DaKi][er /img/forum/go_quote.gif Love the design If i were to do something similar of course I would do things a little different, as the only thing I don't overly like I the charge pump to generate the negative rail when there is already a transformer there to do it, as well as I'm not a PIC person and would either use an 8051 which I know inside out or take the opportunity to pick up an AVR Otherwise it is all round a great design

I could do another bridge/regulator for the negative, but it's actually cheaper (and smaller) to use a charge pump since it needs less than 15mA.

And the ATtiny24 is an AVR.

An 8051 would be quite a bit more expensive.

 

[Polaris111688]

I've been looking for something like this for ages!

 

[splaz]

I'm curious, I don't see why not, using the same external circuitry but different pinout of course, you could use other microcontrollers I'd imagine ?

 

[DaKi][er]

Quote:

Originally Posted by j4cbo /img/forum/go_quote.gif I could do another bridge/regulator for the negative, but it's actually cheaper (and smaller) to use a charge pump since it needs less than 15mA. And the ATtiny24 is an AVR. An 8051 would be quite a bit more expensive.

Center tap the transformer

And somehow I got PIC in my head, guess I didn't read it all close enough

just that all the experience I've ever had in uC's has been with 8051's and I just know them real well and can whip up just about anything in ASM or C, the AVR is dead on perfect for something like this though.

Just one question, how easy are they to program in system? what other hardware is needed? Is it as simple as going through the serial port (via MAX232)?