Power FET

ian field

Joined Oct 27, 2012
6,536
What does CRT era mean?
Actually, we've ordered 5v zener diodes (15 pieces). Here's the link:
http://www.amazon.com/LM78L05-SOT-8...qid=1443902255&sr=8-8&keywords=5v+zener+diode

Is this good?

Also the FET type we ordered is the MOSFET N-channel metal oxide and its drain-to-source voltage is 2.5 kV. Here's the link. Please tell me if it is sufficient. If so, how exactly do I apply it:
http://www.digikey.com/product-search/en?KeyWords=IXTH02N250-ND&WT.z_header=search_go

Thank you.
It appears you are intent on going the wrong way about doing this, and any attempt to steer you in the right direction is going to be futile!
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Our issue is with the load from the ignition coil. It's causing our timer to burn and we need to find a way to enable the NE555 timer to not burn and run well with the load so we may begin experiment. Any advice, given the schematics I've posted along with the resistors and capacitors and diodes, and transistor ordered?
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Yes. Use a step-up transformer (standard vehicle type ignition coil). See post #8.
Alec-t,
Just to clarify, are you saying I should use a step-up transformer since that's what the ignition coil is like? I read about it and I came across a step-down transformer as well, and it said that it allows a low-voltage device to run in a high-voltage environment while the step-up transformer does the opposite. But, we need to step-up the voltage so that it could work well with the load. Am I right?
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Running a simple automotive ignition coil off of a single 555 timer to make a spark generator is easy. Your way over complicating what should be a simple one 555 timer IC circuit and process.

Also when dealing with driving a highly inductive load like a ignition coil off of the same power source as any IC is powered by you need some degree of input power filtering on the positive side to keep the high voltage inductive pulses from getting to the control circuit.

That can usually be done with a simple diode in series with a few ohms to tens of ohms resistor followed by a good sized capacitor on the control circuit side. Lastly adding a diode across the part of the circuit that is controlling the coil across the positive and negative leads going into the coil and out of switching device will help keep the coils inductance currents under control and away form the rest of the circuit.

If done right you should be able to make a highly reliable 20+ KV spark generator with one 555 IC and under 15 components including the ignition coil and switching device. ;)

tcmtech,

I am going to follow your approach. If it's not too much, could you please show me a schematic of where exactly the diodes, resistors, and capacitors and FET should go. I just want to see how everything is connected and compare it to my circuit.

Thank you so much.
 

ian field

Joined Oct 27, 2012
6,536
A standard ignition coil does that for you. It is a step-up transformer. Have a google of 'Kettering ignition'.
My sentiments too - use of a Cockroft-Walton multiplier for spark generators is much less common than a straight step up transformer.

Some high voltage research labs use multipliers to produce millions of volts sparks - but the diode sticks are several times thicker than a street lamp post and the capacitors as big as a car.

A fundamental drawback of the multiplier is that it successively adds the voltage peaks until they reach the top of the ladder, so the pulse generator driving it needs to be at least the multiple of doubler stages higher than the required spark rate.
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Running a simple automotive ignition coil off of a single 555 timer to make a spark generator is easy. Your way over complicating what should be a simple one 555 timer IC circuit and process.

Also when dealing with driving a highly inductive load like a ignition coil off of the same power source as any IC is powered by you need some degree of input power filtering on the positive side to keep the high voltage inductive pulses from getting to the control circuit.

That can usually be done with a simple diode in series with a few ohms to tens of ohms resistor followed by a good sized capacitor on the control circuit side. Lastly adding a diode across the part of the circuit that is controlling the coil across the positive and negative leads going into the coil and out of switching device will help keep the coils inductance currents under control and away form the rest of the circuit.

If done right you should be able to make a highly reliable 20+ KV spark generator with one 555 IC and under 15 components including the ignition coil and switching device. ;)
When I add the diode in series with a resistor and capacitor on the control circuit side, is that located between the output of the timer and the switch? And is that done in the order (from circuit to switch): diode, resistor, capacitor?

Thanks. You're message is very enlightening.
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Running a simple automotive ignition coil off of a single 555 timer to make a spark generator is easy. Your way over complicating what should be a simple one 555 timer IC circuit and process.

Also when dealing with driving a highly inductive load like a ignition coil off of the same power source as any IC is powered by you need some degree of input power filtering on the positive side to keep the high voltage inductive pulses from getting to the control circuit.

That can usually be done with a simple diode in series with a few ohms to tens of ohms resistor followed by a good sized capacitor on the control circuit side. Lastly adding a diode across the part of the circuit that is controlling the coil across the positive and negative leads going into the coil and out of switching device will help keep the coils inductance currents under control and away form the rest of the circuit.

If done right you should be able to make a highly reliable 20+ KV spark generator with one 555 IC and under 15 components including the ignition coil and switching device. ;)

I was confused about something you said about connecting a diode with resistors and a good-sized capacitor. What do you mean by good-sized? Also, the part of the circuit that controls the coil across the positive and negative leads is the output of the timer, right?
 

Thread Starter

Sami Alawadhi

Joined Oct 5, 2015
27
Where in the circuit would I place the FET? After the diode, resistor, and capacitor between the output of the timer and the ignition coil?
 
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