Need TTL Cookbook page 171 & 172. 555 timer 2N3055 vintage Electric Fence Charger

shortbus= said:

And if the coil being used is one of the old round ones used before the advent of HEI type ignitions, you do know it's rated for 6V even though they were in a 12V system. The only time those coils saw 12V was while the engine was cranking over, after starting they had a ballast resistor to run at ~ 6V.

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i used an ignition coil to make a crude ionophone by feeding the primary with the output of an amplifier. it worked ok, but the audio was distorted and had a very large peak at 2khz. an actual ionophone uses high voltage RF across the spark gap (not raw audio like what i was trying). the RF in an ionophone is amplitude modulated by the audio. i expected the audio to be distorted, but was surprised at the 2khz self-resonance of the HV winding (i expected it to be more like 20 or 30khz)

unclejed613 said:

but was surprised at the 2khz self-resonance of the HV winding

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That seems inline with operating range of an ICE, the one that the coil was really made for.

unclejed613 said:

i used an ignition coil to make a crude ionophone by feeding the primary with the output of an amplifier. it worked ok, but the audio was distorted and had a very large peak at 2khz. an actual ionophone uses high voltage RF across the spark gap (not raw audio like what i was trying). the RF in an ionophone is amplitude modulated by the audio. i expected the audio to be distorted, but was surprised at the 2khz self-resonance of the HV winding (i expected it to be more like 20 or 30khz)

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I have another 555 timer circuit with variable frequency driving a 2N3055 that i built about 38 years ago. It is powered by a 6 VAC transformer after rectifier and filter it is about 8.4 VDC. Using the same ignition coil output spark is 1/4" at low Hz probably about 100 Hz. As I turned 555 frequency up the ignition coil must get more efficient spark gets longer and longer up to about 2KHz. Spark length stays about the same from 2KHz to 3KHz. Above 3KHz spark gets shorter and shorter until there is no spark at 5KHz. Ignition coil is not a high frequency device coil becomes less efficient and stops working. Maybe a flyback will work better for audio modulation it is designed for higher frequency. I have a good friend that is into audio he spares no expense for audio equipment. He has 2 electrostatic speakers 6 ft tall 3 ft wide each sound is not very loud but it sounds good. There is a video on Youtube where someone is audio modulating a jacobs ladder music sounds good. I think sound will be better if arc on jacob ladder is not allowed to reach the top then start over at the bottom. Let arc go up and get wider terminate wires with round steel ball so arc stays in place.

gary350 said:

Let arc go up and get wider terminate wires with round steel ball so arc stays in place

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Doing that it would short out the "wires" and no spark would start.

I notice that there is no diode on the collector of the BD139 to protect it from the back EMF from the coil. Therefore it may damage the transistor.
I would put a Zener diode between the collector & emitter. The BD139 has a max CE voltage of 80 Volt. So I would use a 68V 1W Zener. This will reduce the output voltage a little to the fence, but that's better than wrecking the transistor. Also, the base resistor is shown as 1 k. I don't know what the resistance of the primary winding of the coil is nor its inductance. In order to ensure saturation, the base current needs to be at least 1/10th of the collector current.

Nigel Goodwin said:

Why would you imagine a tiny 1N4148 would do the job?, you need a much more powerful diode - without it the transistor may be at risk.

And what's with the pointless ferrite beads?. Also C5 and R8 seem rather strange as well?, the high value of R8 means that C5 isn't doing anything.

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I keep getting conflicting information. 1 person says build circuit on post 26. Another person says use 1N4148 diode from C to E on the 2N3055 for protection. Another person points out 1N4007 is used on circuit 26. Another person says 1N4007 is to slow it will do nothing. Another person says, why you not have C5 & R8 on coil like circuit 26. C5 & R8 are copied form circuit 26. I experiment with all these things then someone says why experiment build it like the circuit. I learn 1N4148 does not last long it becomes a dead short across C & E then circuit no work anymore. Remove 1N4145 diode and circuit works good. I can put 1N4007 across C&E again then someone will say that does nothing. I read online ferrite beads keep HV static out of the circuit. WHAT do you suggest I will give it a try & we see what it does ???

I wonder if everyone making suggestions is reading other peoples suggestions some people accuse me of not reading them.

The 555 circuit I built 38 years ago came from the TTL book. There is no C5 & R8 on ignition coil. There is no diode across 2N3055 transistor. It runs on 8vdc not 12vdc. It has run 38 years and never failed.

gary350 said:

The 555 circuit I built 38 years ago came from the TTL book. There is no C5 & R8 on ignition coil. There is no diode across 2N3055 transistor. It runs on 8vdc not 12vdc. It has run 38 years and never failed

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It hasn't failed because it is running on the 8V that a 12V coil is expecting, that is what the ballast resistor or wire does in a non-HEI ignition or points ignition.

Today I was courious about the 555 circuit I build 38 years ago so I made a drawing. I knew I got the circuit from the TTL book and I probably had a circuit drawing on paper once. D1 & D2 are wired a bit different and R2 adjusts the 555 through a range of frequencies. The power transformer is 6.3 vac it was once used in a tube circuit to power the heaters. My digital meter shows 8.9 vdc from the PS. At low frequency spark is 1/4" long. As frequency increases spark gets longer 3/8" up to about 3KHz then sparks gets shorter to 0 length at about 5KHz. I should probably try this on a fly back transformer some day it will probably make sparks up to 20KHz.