Voltage Shifter

[mlt57sooner]

I am actually pulsing a 555 timer with amicroprossor to give burst of 40 kHz. I would like to pulse the 555 with 12 volts instead of the five that comes out of the processor. I would like to know of a simple way to turn the 5 volts into 12 volts. The voltage shifter circuit also needs to be able to respond to the fast pulses very well. Thanks

 

[David Bridgen]

If you don't need to preserve the polarity of the pulse a single transistor will do the job.

If you do want to keep the same polarity you will need two transistors.

 

[Phasor]

I assume you have the 555 in astable configuration? You can connect the microprocessor output directly to the reset pin of 555 (pin 4). A high signal enables the timer, a low signal disables it.

(The 2khz signal in the screenshot below represents the microprocessor output)

edit: Just realised this is ALMOST my 555th post. That would have been so appropriate...

 

[mlt57sooner]

Transistors?

How would I arrange the transistors? Do you have any example schematics? As for the second reply I have already generated the signal I want I just need it to have a larger pk-pk value. Thanks

 

[Phasor]

I am actually pulsing a 555 timer with amicroprossor to give burst of 40 kHz. I would like to pulse the 555 with 12 volts instead of the five that comes out of the processor.

In that case, I'm not quite sure what you are doing exactly. Got a schematic of your current set-up?

 

[mlt57sooner]

Set-up

I just have the 555 set up to produce a 40 kHz signal and I am turning the 555 on and off with the microprossor. I know that reset lead is supposed to be used to pulse the 555 but I could not get a clean pulse out of the 555 using the reset lead. So I would like to turn the 555 on and off using 12 volts instead of 5 volts.

 

[Phasor]

I think this is what Mr Bridgen was suggesting:
(again, the 2khz signal represent the uP output)

 

[David Bridgen]

What a strange thing to do Phasor.

All your circuit does is apply a 1k load to the 555 2,000 times a second.


No. What I meant is something like this:

 

[Phasor]

What a strange thing to do Phasor.

Ah yes, what was I thinking?? As Ron H would put it, I had a Brain Fart.

 

[David Bridgen]

Yes, I have them myself.