# Looking for a High-voltage power supply

Joined Oct 5, 2015
27
We are trying to build a spark ignition circuit and we were interested in the capacative discharge circuit. Our switching device is a monostable NE555 timer circuit for purpose of regulating time and our ignition coil steps up the voltage to 20 kV to ignite the spark plug. Does anyone recommend a good high-voltage power supply to charge the capacitor? We were considering a 450-V power supply.
Here's a link for a capacitive discharge circuit. It has the schematic: http://www.daytona-twintec.com/tech_ignition.html
The PDF and schematic for our NE555 timer is attached.

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#### AnalogKid

Joined Aug 1, 2013
10,113
I put 'cd ignition schematic' (without quotes) into Yahoo and got over 100 schematics.

ak

#### crutschow

Joined Mar 14, 2008
30,450
What power source do you want to use to generate the 450Vdc?

Joined Oct 5, 2015
27
What power source do you want to use to generate the 450Vdc?
no more than $250. #### crutschow Joined Mar 14, 2008 30,450 no more than$250.
The cheapest would likely be to get a small transformer with about a 320V output (such as this) and then full-wave rectify that with a bridge and filter to get 450Vdc.
The device I referenced also has a couple of 6.3V windings which you can use in series to add or subtract up to 12.6V AC from the 320V output if you want to tweak the output voltage. It also has a 300V tap.

Does the voltage need tight regulation?

What is the maximum pulse rate of your circuit?

#### ian field

Joined Oct 27, 2012
6,536
The cheapest would likely be to get a small transformer with about a 320V output (such as this) and then full-wave rectify that with a bridge and filter to get 450Vdc.
The device I referenced also has a couple of 6.3V windings which you can use in series to add or subtract up to 12.6V AC from the 320V output if you want to tweak the output voltage. It also has a 300V tap.

Does the voltage need tight regulation?

What is the maximum pulse rate of your circuit?
For that sort of budget; it might be just as easy to buy a CDI unit and hack the intermediate voltage without using the trigger/SCR/capacitor discharge bit.

The inverters usually produce somewhere in the region of 350 - 400V, but can probably be tweaked to get the required voltage.

A very important point: do a bit of research and make sure the "best candidate" isn't potted before parting with the money.

#### crutschow

Joined Mar 14, 2008
30,450
For that sort of budget; it might be just as easy to buy a CDI unit and hack the intermediate voltage without using the trigger/SCR/capacitor discharge bit.
................
But those usually require a 12V dc input when also has to be generated/provided.

#### ian field

Joined Oct 27, 2012
6,536
But those usually require a 12V dc input when also has to be generated/provided.
There was nothing in the original post to suggest that the energy source was to be magicked out of thin air - in fact the link was to an explanation of automotive ignition systems, although 12V supply wasn't specifically mentioned, it seemed a reasonable assumption in light of the few facts supplied.

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088

#### recklessrog

Joined May 23, 2013
985
Go to the "information unlimited" web site and download the schematic for a universal capacitance discharge ignition (CDI) driver" That one will blow your socks off! Up to 50-70Kv depending on the ignition coil you use, and it's adjustable. I built one using the cores from an old B&W portable tv line o/p transformer.