Analog issue

**Acetronics2** · - 17th March 2009, 14:54

Hi, JM

That looks to be dealing with high voltage ... and very high instant currents.

May be also a switching up converter to think to ...

soooo ...

are you REALLY sure there's no spike on either an ADC input or 5v supply rails ???

could we have a piece of scheme showing the Fet's drive and the ADC inputs ???

Alain

**jmgelba** · - 17th March 2009, 15:13

There could be spikes - I have yet to measure for that. And yes, we are switching 2 channels, both at 760W each. 24v at 31.6 Amps.

I'd have to ask the whole forum to sign an NDA to show you the schematic, but the 5v line has a lot of capacitance but the inputs do not as I cant wait for the line to charge. From input pulse to output on needs to be less than 35uS. My customer wanted 5uS or less originally!!

**Archangel** · - 17th March 2009, 15:59

Originally Posted by jmgelba

My customer wanted 5uS or less originally!!

Make it so . . http://www.realmagicwands.com/

**jmgelba** · - 17th March 2009, 16:02

Just measured for spikes - there are some small ones on the 5v line lasting in the uS range. Largest I've seen was 0.341V. ADC line is dirty. I'm sampling for 20uS. I'll put a .1uF and a 1nF on there and see what happens.

I put a 10ms delay at the end of the flash subroutine and so far that looks to be working.

**Acetronics2** · - 17th March 2009, 16:23

Hi,

One thing you easily can do is lock your inputs as soon as Fets fired ... you have the time the capacitors charge for gliches " hiding" ...

I'll search on my HDD ... there's an old Elektor project of a ... discharge capacitor welding machine for NiCads ...

Your application HardW should not be so far from that !!!

Alain

**jmgelba** · - 17th March 2009, 16:49

Hmm have a problem else where. Just to verify my 10ms delay was working, I increased it to 1000ms. Now the flash (FET's)does not respond to the input. I can send a pulse and nothing happens, then I get lucky some times. Turns out that the program is running and pausing for 1000ms as though there has been a pulse sent.

So the problem I have is it is running through the whole program and not returning to MAIN and waiting for a pulse.

Code:

IF (BNK1 => 466) OR (BNK2 => 466) THEN FLASH
goto MAIN

This should make the program jump back to the start of MAIN unless the ADC is 466 or higher, right?

Code:

FLASH:
IF PORTA.4 = 1 OR PORTA.5 = 0 THEN 
PORTB.0 = 0 : PORTB.1 = 0 : PORTB.3 = 1
endif


IF DUR = 1 THEN 
PAUSE 1
endif
IF DUR = 2 THEN 
PAUSE 2
endif
IF DUR = 4 THEN 
PAUSE 4
endif
IF DUR = 8 THEN 
PAUSE 8
endif
PORTB.0 = 1 : PORTB.1 = 1 : PORTB.3 = 0
PAUSE 1000
GOTO MAIN

the program is running the FLASH routine without actually sending a pulse out to the FETs unless one of the inputs is triggered. I know this because I can measure the time delay between applying an input signal and waiting for an output.

So my question is, why is there up to a 1 second delay between applying a signal and getting an output?

**jmgelba** · - 17th March 2009, 16:52

Nevermind - I see it. The flash routine will only fire the FETS if there is an input, it will still run the routine if there is an input or not. OK, so, how do I get it to go back to the start of the program if there is no input rather than go through the whole flash routine and wait that 1000mS?

**Acetronics2** · - 17th March 2009, 16:57

Got it !!!

I only can pass the program ( AT Tiny ...) but it can give you some ideas.
the article with scheme ( nothing special ) is 400 kb ..

But you can retrieve it from the english Elektor site. ( year is 2006 )

Alain