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F5 Micro (A useless but funny project)
F5 Micro (A useless but funny project)
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Old 14th June 2011, 10:14 PM   #1
Nikon1975 is offline Nikon1975  Austria
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Default F5 Micro (A useless but funny project)

Dear All,

I started to play with the Arduino microprocessor (Had not use any microprocessor before), and I was amazed to find out how easy is to implement things using it.

I was thinking, how difficult can be to make a controller for the F5 ? My idea is to spit my project in two phases:

1) Passive: Arduino reads temperatures, offset, and bias and show them on a display or gives alarms.

2) Active: Arduino reads all the parameters, protects the speakers from excessive DC offset and allow to modify the bias. I would do first with an algorithm to be used with speakers disconnected and if it's really reliable it could be done real time.

This would be fun for listening tests and to find the sweetest spot. The F5 was selected only because I am familiar with the circuit and with the behavior while setting the bias.

Here is where my basic electronic ignorance come into the game, and I would appreciate to have some hints on what parts or circuit should I use for:

a) Measuring a voltage that is not between 0 and 5V but between 23V and 24V.

b) develop a controlled resistor.

c) measuring the DC bias

I am not asking for ready made things, just to be pointed where to start my readings.

Any collaboration in this project is welcome !!!

By the way, I found out that having a display on a device can largely increase the WAF of the device. You can program the amp to say sweet thing to your best half, any time it powers up. No commercial amp can do that !!! They will love it.

Best Regards,

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Old 14th June 2011, 11:05 PM   #2
nigelwright7557 is offline nigelwright7557  United Kingdom
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I use a PIC micro for checking DC offset and for power up delay on the speaker relay.
If I see 500ms of DC I assume there is a fault and disconnect the speaker relay.

You can use an a2d converter for looking at voltages.
You could use scaling resistors to look at higher voltages but you would lose accuracy that way.
Murton-Pike Systems PCBCAD51 pcb design software. http://www.murtonpikesystems.co.uk
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Old 15th June 2011, 12:08 AM   #3
Bksabath is offline Bksabath  United Kingdom
Join Date: Dec 2007
Hi Nikon

IMO change the tread title to a Useful and Funny...

I am to green to realy help but will be watching

At present I have one transistor for power up (momentary Push Button)
One transistor timer for Thermistors By pass.
NTE 7100 for speaker protection which does delay speaker conection
DC ofset protection and speaker disconect when power down (before thump)
It could also do overcurrent but I have not implemented that.

I was going to try for overcurrent protection by reading the voltagge accross the source resistors with a couple of comparators but not there so far.

SO I will be watching this.

To have all this on a single board (NTE7100 obsolete) is a great idea.

All the best

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Old 15th June 2011, 05:10 AM   #4
digits is offline digits
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I've often thought about adding miscroprocessors to amps, but then I am stumped by how to realy isolate the clock noise etc from the digital side going to the amp side.
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Old 15th June 2011, 06:11 AM   #5
derwhalfisch is offline derwhalfisch  New Zealand
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Nikon - awesome. Arduino is a lot of fun. I suggest:

Read the API for libAVR. I think most of the AVR variables and functions can be accessed from inside the 'Wiring' and 'Processing' based IDE they provide you for programming your Ardy, or you can code in C/C++ and compile with the IDE. Their basic implementation is very limited. It works and is easy, but there's so, so, so much more your ATMEGA chip can do.

Get the big, fat manual for whatever chip your Ardy has on it. You're going to be using the ADC a lot, and you'll find out by reading the manual exactly how limited and slow the Arduino IDE's ADC API is. You can achieve 8-bit sampling at about 70kHz on the ATMEGA168 if you get at it directly using AVR's functions. Also, there are... 3? Hardware and ...3? timer interrupts available so you don't have to use the 'delay' function (which is really just a "wait X cycles" loop) and I2S and SPI etc etc etc interfaces available for talking to DAC's and DSP's and blahblahblah

Makes me want to buy another. Mine got blown up when I lent it away to be used in a highschool production controlling lights :'(
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Old 15th June 2011, 12:26 PM   #6
Nikon1975 is offline Nikon1975  Austria
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Thanks for the support! The display and remote command part with Arduino, I already figured out for my DAC. Where i am lost is the measurement of the voltages not referenced to zero and the offset.

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Old 16th June 2011, 02:52 AM   #7
derwhalfisch is offline derwhalfisch  New Zealand
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Which version of Arduino do you have? Which ATMEGA chip, more specifically?
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Old 16th June 2011, 04:28 AM   #8
Nikon1975 is offline Nikon1975  Austria
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I am not sure ATMEGA168 or 328.

I'll check.

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Old 16th June 2011, 05:41 AM   #9
qusp is offline qusp  Australia
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very cool Davide!! you could perhaps use LED's for the bias (variable resistor) and control these with voltage?
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Old 16th June 2011, 05:59 AM   #10
EUVL is offline EUVL  Europe
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It sounds like real fun.

A personal opinion if I may :

A uP based solution will have all the flexibility in the world, and you can change things easily even after the hardware is in place.
In that sense it is hard to beat.

We had a similar discussion at work about a safety concept for a semiconductor manufacturing equipment a few years back. The consequence of a crash is over a million Euro damage. Not as bad as in a nuclear plant, but also the company's reputation is at stake in such a crash. After a long discussion of over three months with more than 20 conceptual system architects involved, we finally went for a safety solution which is purely mechanical and electrical hardware based (crash barriers, safety traps, electrical hard wired interlocks, ...).

I am sure you also know a few such examples at work.

If I were to choose, I think I'll still go for the hardware solution.
If anything, I don't think I want a MHz oscillator near my analog Amp.

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