Pulsed DC reverse enginering

[b9creations]

Hello,
I have a corona discharge device and working on building another based on the original unit. The circuit board seems rather simple, pulses voltage and delivers that to coil.

I guess I need to get o-scope to check for the pulsed frequency, but trying to determine if it's pulsed AC or DC voltage. The O-scope I have in mind for purchase does not do ac coupling. So if it's AC I need a more expensive o-scope OR need to have the board sent out to for analysis to electronics expert.

Any ideas on how I can determine if the pulsed voltage going to the coil is AC or DC before buying the Hantek 6022BE PC based O-scope? The voltmeter gives a reading for both AC and DC. AC reading is higher. When I switch leads it does not show negative voltage reading (when in DC mode on the voltmeter). Perhaps this is not enough to go on? My hunch is it's DC since there is a large rectifier on the circuit board but want to be 100% sure.

Thanks very much for any advice, tips, or pointers.

Best regards Ken

 

[chuckey]

I would think that it will be a DC supply which is switched on and off by some sort of transistor. So if the transistor switch is in series with the DC supply then when the switch is on, current will flow into your coil. The remaining problem is to limit the current somehow, it could be by using very short pulses and effectively a big coil, so the current never reaches its maximum, before the switch is turned off or could just be a series resistor somewhere.
Frank

 

[b9creations]

Thanks Frank. With more research am finding pulse rates vary between about 40 to 400 PPS with a duration of 5-500 nanoseconds. I wonder if it would be possible to modify something like this to do the job?

https://www.amazon.com/Unique-Goods...ywords=unique+goods+dc+motor+speed+controller

Or perhaps this?

https://www.amazon.com/Unique-Goods...ywords=unique+goods+dc+motor+speed+controller

Like I said, I am pretty much newbie when it comes to all of this, may be way off track.

Voltage that feeds the coil is really low, but like I said can't tell if it's AC or DC without a scope.

Thanks again for any and all comments/help. Greatly appreciated.

Ken

 

[chuckey]

First item, PWM frequency = 500 HZ, so time for one cycle = 2mS. The pulse can be as short as 5% of this, which is 10 micro seconds. The second one has no PWM frequency listed.
The pulse period is a definite problem, you need some really fast switches to be able to go then off within these sort of periods. Like about one thousand times faster then the Amazon examples!
Frank

 

[b9creations]

Awesome Frank! Thanks so much for that info, thank you thank you. I was under the impression 500Hz meant 500 ppm which is obviously far from the case. : )

So looks like I may be dead in the water for now.

The original plan was to try this adjustable frequency square wave device here on ebay: **broken link removed**

The main chip: LM358.
The frequency adjustment range: 0.07HZ-2KHZ (also cycle in about 0.45ms to 15s).
Duty cycle adjustment range: 0% to 100% (High / cycle).
Output Current: strip 9012 transistor drive capability is only 500MA output current though.

But looks like even this does not go fast enough either then?

I went ahead and ordered the PC based scope, a variable power supply, amp clamp, breadboards, etc.

I figure if I can at least get lucky enough to determine the precise pulse rate and the voltage/amperage I have a starting point to work from.

The circuit I am trying to emulate is very basic. Just power supply comments, (voltage regulator, bridge diode, a few misc diodes, zener diode a couple caps and of course an 8 pin IC that (12c508a 04p) that creates the pulse.

But obviously that is a programmed chip so well beyond my capabilities to replicate that. Looks like a long road ahead but very excited to be learning how to eventually make this happen!

Smiles and gratitude, Ken