Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

24V Inverter Circuit?

Iawia

Member
Hi Guys,

Is there a circuit that can invert a 24 volt signal? Everything i have found is so far is limited by voltage (ie inversion circuit using 555 timer can do 16V).

Hence when the signal is 24v, I need an output of 0, when it is 0 output needs to be 24v. I need less than .02 A for amperage per signal, i have 3 signals that need to be inverted.

Much appreciated.
 
Hi Guys,

Is there a circuit that can invert a 24 volt signal? Everything i have found is so far is limited by voltage (ie inversion circuit using 555 timer can do 16V).

Hence when the signal is 24v, I need an output of 0, when it is 0 output needs to be 24v. I need less than .02 A for amperage per signal, i have 3 signals that need to be inverted.

Much appreciated.
You can do that with a single transistor and a for each data line.

Assuming your load is actually taking in 20mA (the 1.2k resistor is your 20mA load.

If it's not drawing any current snd just a jfet input, you'll need a pull-down resistor to drain any charge (add a 10k resistor to the PNP output).

IMG_5872.jpeg
 
Hi Guys,

Is there a circuit that can invert a 24 volt signal? Everything i have found is so far is limited by voltage (ie inversion circuit using 555 timer can do 16V).

As usual, a 555 would be a really poor choice.

Hence when the signal is 24v, I need an output of 0, when it is 0 output needs to be 24v. I need less than .02 A for amperage per signal, i have 3 signals that need to be inverted.

Much appreciated.

It's extremely simple to do, but we need EXACT details of the circuit, exactly what's feeding the inverter, and what the inverter is feeding as well, plus what ever power supplies are involved.
 
How close does the output need to get to 24 V and to 0 V?
It does not need to be too close, they are interpreted as data bits which command a motor (enable, command, fwd/rev). Technically, the signal can be between 5-24v ... I prefer to keep it nominal if that is feasible. My signals work, however to command the motor are from a sinking PLC which provides a 0v instead of 24v. That is my issue, rather than purchase a sourcing PLC, i was hoping to resolve it with TTL, I can avoid the long wait and beauracracy of ordering at work.

1737227370762.png
 
Yes, you can invert a 24V signal using a simple NPN or PNP transistor with pull-up or pull-down resistors. This solution will work for your low current (less than 20mA) signals and will allow the output to switch between 0V and 24V as needed. Since your signal is from a sinking PLC, this should resolve the issue without needing a sourcing PLC or a 555 timer.
 
Yes, you can invert a 24V signal using a simple NPN or PNP transistor with pull-up or pull-down resistors. This solution will work for your low current (less than 20mA) signals and will allow the output to switch between 0V and 24V as needed. Since your signal is from a sinking PLC, this should resolve the issue without needing a sourcing PLC or a 555 timer.
Thanks Zone, and would you be able to provide the circuit? I am ready to build it and test!
 
Thanks Zone, and would you be able to provide the circuit? I am ready to build it and test!
The circuit they are talking about is already drawn in post#2 above (as the PNP transistor version).
 
You may also be able to use a comparator of the LM339 (Quad) or LM393 (Dual). Put your reference on the + input and your input on the minus input. You can also add hysteresis and don't forget a pullup resistor on the open collector output.
 
You may also be able to use a comparator of the LM339 (Quad) or LM393 (Dual). Put your reference on the + input and your input on the minus input. You can also add hysteresis and don't forget a pullup resistor on the open collector output.
Unless there is a pull-down on the input of his device. All of the suggestions need more information from the OP to implement.
 
You can do that with a single transistor and a for each data line.

Assuming your load is actually taking in 20mA (the 1.2k resistor is your 20mA load.

If it's not drawing any current snd just a jfet input, you'll need a pull-down resistor to drain any charge (add a 10k resistor to the PNP output).

View attachment 148519
Hi Zip, hmm i can't get this to work. i recognize that the PNP collector and emitter get swapped from what I normally use (NPN), I am using 2N3906 which maybe there is an issue with the 24V? I can't tell but it says base to emitter can only be 5v. Should i be using a different one?
 
Add a 1K between base and emitter at the transistor.

With only a 10K base resistor, the input being just 0.6V lower due to signal levels or leakage will start to cause the transistor to conduct.

With 1K at the base to emitter, the signal to the 10K would need to be around 6V lower than the 24V supply to start to cause conduction. That should make it more stable and reliable.

(The 10K only version would be fine if the input was actively driven to +24V when in the high state, but not for a pull-down output with no definite high level itself).

If the PLC output is leaky, it may still need additional load resistors directly from the PLC outputs to +24V to ensure a good stable high level when they are intended to be high.
 
Hi Zip, hmm i can't get this to work. i recognize that the PNP collector and emitter get swapped from what I normally use (NPN), I am using 2N3906 which maybe there is an issue with the 24V? I can't tell but it says base to emitter can only be 5v. Should i be using a different one?

As I said in post #6, without knowing exactly what is at each end people are just guessing in the dark - but you're probably going to need 0v, +ve, and signal at each end. PLC's often have opto-isolation as well, which adds a potential further complication.
 

Latest threads

New Articles From Microcontroller Tips

Back
Top