Years ago I thought of using a car ignition coil as a single ended output transformer and just yesterday I looked it up and sure enough several people have already done it. Most distributor-type coils are 100:1 and newer ones will easily tolerate 6 amps in the primary, though not continuously. 3 amps would probably be okay. That means for a 100:1 coil 30mA in the HV side would be just fine. Many have a resistance of about 6000 ohms so you are going to drop 180V. Starting to look like a loser of a project already but practicality is not the name of the game here. The point is to see if it can be done and how good / bad it works.
First off is frequency reponse. I had a pair of identical 65:1 coils that have 3500 ohm resistance HV side and pumped a signal from an amplifier into the LV winding and fed the HV output into the HV winding of the second coil and them put the scope across the LV output of the second coil. Loaded it with a 10 ohm resistor.
Started of at 1kHz with an output of 8V p/p then measured in steps to 20kHz. Then started to go from 1kHz down but coil started to run out of reactance and pull to much current so I changed it to 0.8V p/p for frequencies under 1kHz. To express it in dB I just got the base 10 log of the voltage and then multiplied it by 10 to make the graph look nice. I hope that is kind of right. The response is of two coils cascaded, not one by itself.
First off is frequency reponse. I had a pair of identical 65:1 coils that have 3500 ohm resistance HV side and pumped a signal from an amplifier into the LV winding and fed the HV output into the HV winding of the second coil and them put the scope across the LV output of the second coil. Loaded it with a 10 ohm resistor.
Started of at 1kHz with an output of 8V p/p then measured in steps to 20kHz. Then started to go from 1kHz down but coil started to run out of reactance and pull to much current so I changed it to 0.8V p/p for frequencies under 1kHz. To express it in dB I just got the base 10 log of the voltage and then multiplied it by 10 to make the graph look nice. I hope that is kind of right. The response is of two coils cascaded, not one by itself.
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I wouldn't be shocked (heh) if a high-performance coil, meant for high RPM racing, would perform better.
Circlo - thanks for doing that! I've often wondered.....
The big safety concern might be that these are autoformers, not real transformers with separate windings. Going up might not be dangerous, but going from HV to LV might be.
Now that said, what would you use it for? Running an electrostatic midrange? A talking flame or plasma speaker?
The big safety concern might be that these are autoformers, not real transformers with separate windings. Going up might not be dangerous, but going from HV to LV might be.
Now that said, what would you use it for? Running an electrostatic midrange? A talking flame or plasma speaker?
This is a pretty solid coil in fact -> 4200 Pro Series Race Ignition Coil - ICE Ignition With 10 amps switched in the primary I have measure 160 millijoules actually delivered to the spark gap. Compare that to a MSD6 CDI that puts out an advertised 100 millijoules to the coil but only 35 millijoules actually makes it to the spark gap.
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