Switching using 3055 transistor

Thread Starter

obbyt

Joined Mar 25, 2020
8
Hi guys, I have seen a fair bit of posts similar to the help I am requesting, but with enough variances that I felt I should just come out and ask.

Basically, I am trying to take a signal coming out of a 555 timer, pass it through a 4017 decade counter to achieve a led sequencer type output, but instead of lighting up leds, I need to activate high voltage transformers. The output of the 4017 is not adequate, so I decided to try and pass that signal through a 3055 transistor in a switching circuit style, to turn on and off the transformers using one or two 3.7v lithium batteries feeding the collector/emitter.

I believe I attached a pdf of a similar schematic that someone else on here is working with, trying to get fireworks to go off in a similar manner as my circuit, but I don't recall an answer that worked for mine. In the supplied pdf, on first page, the 555 and 4017 part of the circuit works fine. The main difference between my circuit and the pdf is instead of 24v secondary input, I am using just one or two batteries rated at 3.7v each. As well, in my circuit the only thing I have above the collector is the batteries and the transformer, nothing else, the schematic is just for reference to show you what I am dealing with.

For some of you, you will shake your head after looking at it thinking it is a simple fix, but I have been staring at this problem too long and I need a second set of eyes to see it clearly. For the base resistance, I am using a 100 ohm resistor between input signal and base, emitter grounded out, and latest attempt of running 3.7v through the transformer in series to the collector. I do get some power coming out of the transformer (slight sparks when output wires touch, but desired output of spark gap from output wires is a couple centimeters and approximately 200kv - 400kv. So, obviously I am getting power running through, but not enough current? maybe not enough voltage? Not sure. It's been a while since I dealt with switching circuits and my mind is turning to mush and would love some help.

Thanks for any ideas,

Oz
 

Attachments

Thread Starter

obbyt

Joined Mar 25, 2020
8
Hi, thanks for replying. No, I am using just a 100 ohm resistor. The 3.9k was what the other guy was using that created that schematic. After the base resistor, the only thing that is the same as mine is the transistor. Base resistor is 100 ohms, emitter is grounded, and on top of collector I have 3.7v battery feeding through a transformer then attaches to collector. If that makes any sense to you
 

Thread Starter

obbyt

Joined Mar 25, 2020
8
There is nothing practical about the circuit I am making. I created a circuit with a number of spark gaps, but at the moment the gaps fire randomly and I desire to control them so they go off sequentially. I can't control the high voltage side, so I am manipulating the lower power side of the transformers.

At the moment, I am using all tip3055 transistors because I am trying to keep the circuit light weight and compact. The circuit, I am sure could be streamlined, but at this moment in time I am at a loss of how it could be done. Once I get a single transformer activated fully via the sequential circuit, I should be able to duplicate the result for the remaining transformers.
 

BobTPH

Joined Jun 5, 2013
2,349
With 3.7V through a 100 Ohm resistor you will get about 30mA through the base or about 300 mA through the collector.

What is the transformer ratio? The current is reduced by that same ratio. So, if you were to try to get 1000V you would get 1 mA.

Bob
 

Thread Starter

obbyt

Joined Mar 25, 2020
8
I believe I measured the output of the 4017 to be closer to maybe 1.5v to 2v (hard to get reasonable measurement due to the decade counter output moving around). The transformer has an input range of 3.7v - 7.4v and an output range of 400kv to 600kv.
 

BobTPH

Joined Jun 5, 2013
2,349
The transformer has an input range of 3.7v - 7.4v and an output range of 400kv to 600kv.
That is not a simply transformer then. It is some kind of high voltage generator.

How much input current does it require?

Can you post a link to specs for it?


Bob
 

Thread Starter

obbyt

Joined Mar 25, 2020
8
Before I make any further changes, this is where my circuit is at the moment. It seems using that other circuit someone else created was a bit confusing because my circuit wasn't exactly like it. So, I created this one using multisim and now you can see exactly what I have in front of me.

Bob, you are correct. Technically this is not a transformer, but a high voltage generator. It is one of those high voltage modules you see on amazon or ebay, typically from china. Specs are a bit vague as they don't supply much info on it. Input is generally 3.7v (but can handle up to 7.4v), I can't get a proper reading of current probably due to internal components which I cannot see (epoxy encapsulated). It is a bit frustrating dealing with this circuit.sequencer.gif
 

Audioguru again

Joined Oct 21, 2019
1,289
Your 4017 has no power supply voltage shown. If it is only 3.7V then its output is 3.7V only when it has no load. The 100 ohm resistor in series with the base of a transistor with the emitter grounded is almost like a dead short to it.

The datasheet of a CD4017 and most other CD4xxx ICs is very low as shown on their datasheets.
Here is the output current of the CD4017 feeding directly (no resistor) into the base of a silicon transistor:
 

Attachments

Thread Starter

obbyt

Joined Mar 25, 2020
8
Atfer, thanks for pointing that out, I forgot to omit a wire because originally I had a power source connected on the left side then removed it but forgot to remove a wire after. I believe the updated schematic should be proper.sequencer.gif
 

Audioguru again

Joined Oct 21, 2019
1,289
Did you see my post that the output current from a CD4017 is Way Too Low to drive a power transistor in your circuit?
How much current does the transformer primary winding need? 3A is 3000mA but you are getting 20mA to 100mA.
 

Thread Starter

obbyt

Joined Mar 25, 2020
8
Audio, yeah I read it. I was just sitting here staring at my circuit trying to figure out how to make it work. Thanks for info. As for the minimum current to make transformer work, I am not sure. It works great using a 3.7v 2000mah lithium battery, but how much current it is actually pulling i am not sure.
 
Last edited:

Audioguru again

Joined Oct 21, 2019
1,289
Current= Voltage divided by Resistance. Simply measure the Resistance of the primary winding and measure the Voltage of the battery when it is powering the winding. Then C= V/R.

If you put a current meter in series then the reading is wrong because the meter uses some of the voltage causing the current reading to be low.
 

BobTPH

Joined Jun 5, 2013
2,349
@audio
Current= Voltage divided by Resistance. Simply measure the Resistance of the primary winding and measure the Voltage of the battery when it is powering the winding. Then C= V/R.
It is not a transformer. See in post 12 his response to me. It is a high voltage boost converter, probably this one or similar:

400 KV boost converter

And @obbyt, notice this in the specs for the one I linked:

- Input current: 2 A - 5 A
Bob
 
Top