Author Topic: Simple TTL signal generator/counter with sum  (Read 584 times)

Offline PekkaNF

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Simple TTL signal generator/counter with sum
« on: February 19, 2018, 04:19:33 AM »
This probably has a name, but can't really pin it!

I have a traditional cheap sine/triangle/square 12M or so signal generator. It has sweep etc. but it does not have a setting that I can simply send out exact amount of pulses.

There must be a simple product somewhere?

I can see very complicated arbitary signal signal generators that can produce all sorts of serial communication protocols etc. some even tempting cheap, but they need laptop and to learn a new scripting language and all that extra.

I remember when I was studying we had all that lab equipment that would do stuff and we could use simple counter/pre scaler with gate-function to count the pulses from generator and gate some multiples of ten out.

Could cobble out arduino stuff....but I see myself on doing this increasingly offten and I', looking at the signal generator trigger and TTL BNC connectors and thinkking one more little box....even if I have to solder together some eBay specials.

Now my needs are modest:
* TTL-level input/output, a little of overvoltage/negative voltage protection or buffer on socet would be nice
* Modest speed, generally 100 kHz or so would be most of the time enough
* Amount of pulses random: one to least 2k
* own simple TTL pulse generator plus, but I have one that has two output PWM, phase angle and all that.


I checkked the manual of my generator and it does not provide this simpply. Apparently I could learn another scripting language, do it on PC, hook it up on my signal generator and play it out....but I am such a old timer that I rather not.

Pekka

eskoilola

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Re: Simple TTL signal generator/counter with sum
« Reply #1 on: February 20, 2018, 03:13:46 PM »
I am not sure whether I understood Your spesification correctly.

So You want to get a defined amount of pulses triggered by some input.

Nowdays one would harness a small microcontroller to do that sort of a task. It probably would take less space than a dedicated IC circuitry.

So.

Using AD converter to adjust the number of pulses. Another AD as the frequency setup. One input pin as the trigger and another as the output. PIC18F25would be my choise for this kind of a task.

This MCU can be clocked to 64MhZ by it's internal RC oscillator and one can put it into sleep while not doing anything. (Wake up by INT0).

Instead of scripting You would find Yourself doing some MCU code ... and as You are an Oldtimer - probably with assembler :)



Offline awemawson

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Re: Simple TTL signal generator/counter with sum
« Reply #2 on: February 20, 2018, 03:52:34 PM »
Parallel port on an old PC running DOS and QBasic and poke your required data as you wish - simples  :med:
Andrew Mawson
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Offline PekkaNF

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Re: Simple TTL signal generator/counter with sum
« Reply #3 on: February 21, 2018, 02:45:39 PM »
uuh...wanted to buy a small PCB and use BCD wheels or something binary/decimal counters and all that....kids in the office said why would you not use arduino.... :lol:

OK. Problem solved this time.

But one furher question....if I want one:
* More crisp edges faster/more sink/source current than those GPIO's produce?
* Want open collector output?
* Want not only TTL, but those new sissy 3,x voltages out?

Old time just put the whole DIL-buffer and all outputs parallel. Choose the buffer that I fitted and found on the corner shop.

Pekka

Offline AdeV

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Re: Simple TTL signal generator/counter with sum
« Reply #4 on: February 22, 2018, 08:08:53 AM »
Sounds like an ideal application for a smallish FPGA; but I don't know if you can get those in "hobbyist friendly" formats (i.e. DIP).
Cheers!
Ade.
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eskoilola

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Re: Simple TTL signal generator/counter with sum
« Reply #5 on: February 22, 2018, 11:34:45 AM »
Well. One can, of course, harness an entire buffer to output the needed power. Another option would be to use small low threshold N and P fets connected fae-to-face. Of course one needs some sort of current limitation as these WILL conduct at same time, being a very short time that could be two tiny inductors.

I made a largeish FET gate driver circuit that was capable of outputting 15 V/pp into a 0.47uF capacitor @ 10KHz. The test capacitor fried - of course - just in 2 seconds. The output current was in the 20A region. This kind of circuitry is needed when FET array (many fet's in parallel) need to be switched on/off very rapidly. In this case the array consisted of 27 high current, medium voltage FET's. The gate capacitance was 0.1uF all together including the miller capacitance. The driver used the face-to-face FET topology which I have found to be quite easy to get going.

Offline PekkaNF

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Re: Simple TTL signal generator/counter with sum
« Reply #6 on: February 22, 2018, 05:45:50 PM »
My signal generator sucks.

Need better buffer for TTL. Would something like this do? Sans oscilator



Testing small test probe, idea from here:
http://jahonen.kapsi.fi/Electronics/DIY%201k%20probe/

Put some pogos on dupont connectors. These will hook on normal pin strip and on most connectors.