24V to 5V

[heepofajeep]

Hi, stupid question (lol, one of these days maybe I will be electronically inclined enough to ANSWER the stupid questions rather than contributing ): A proximity sensor I am using is switching 24V. The controller I am using can only handle 5V ttl signals... So I just need a simple device to step from 24V to 5V.

Thanks!

 

[audioguru]

A simple 5V voltage regulator IC will work if the current is 1A or less and you cool it with a large enough heatsink.

But you didn't say how much current.

 

[Hero999]

If you don't need the current and you want to save space & money there's the 78L05 which can supply 100mA.

 

[Papabravo]

I think what you want is a comparator, like an LM393 or LM339. The 24 V inputs are no problem and the output being open collector can be pulled up to your 5V supply. Make sure that at least one input is within the common mode range.

 

[audioguru]

If you don't need the current and you want to save space & money there's the 78L05 which can supply 100mA.

It cannot supply 100mA with 19V across it. Its internal temp would try to be about 462 degrees C. Its absolute max internal operating temp is only 125 degrees C.
A 7805 in a TO-220 case will be just barely not able to pass 100mA with 19V across it without a heatsink.

 

[audioguru]

An ordinary transistor could have two resistors at its base for a 24V swing and its collector connected to the TTL input with a pullup resistor.

 

[Dr.EM]

I'm not sure if he's only stepping the signal levels down? In which case a simple resistive divider should do, though being TTL it may require buffering afterwards.

 

[dknguyen]

It seems some people are misreading the question as a DC-DC converter power supply queston)


I would use an op-amp comparator with a resistive divider on the inverting input of the op-amp. The divider ratio is dependent on the logic high/low threshold of the 24V signal to step down the signal so if for some reason the logic level threshold is not proportionally the same between 24V and 5V you could account for it.

A resistive divider and op-amp buffer (an op-amp with a single loop connection- really simple) would work too if the logic thresholds between the 24V and 5V signals were ratiometrically the same.

 

[Oznog]

Yeah, he says he has to level shift a signal, not a power supply!

Actually a 5.1v zener and a 10k resistor should probably do it. Cheap, dirty, effective.

 

[William At MyBlueRoom]

The LM2574 simple switcher works like a charm.

 

[heepofajeep]

Lol, what an awesome response . Although now I have a lot of research to do to understand half the responses, lol (still working on my electrical knowledge).

To clarify, I will be using a 24 Volt powersupply (I think it *can* supply 6amps, not that it matters) to an Omron Proximity sensor (I will try & pull up the spec for the sensor in the morning), and the NO sensor will switch closed when the object is sensed. I need the corresponding 24V signal to then be 'scaled' down to 5V so that my motor controller can understand the sensor is sensing the object

Thanks again!

 

[Nigel Goodwin]

Lol, what an awesome response . Although now I have a lot of research to do to understand half the responses, lol (still working on my electrical knowledge).

To clarify, I will be using a 24 Volt powersupply (I think it *can* supply 6amps, not that it matters) to an Omron Proximity sensor (I will try & pull up the spec for the sensor in the morning), and the NO sensor will switch closed when the object is sensed. I need the corresponding 24V signal to then be 'scaled' down to 5V so that my motor controller can understand the sensor is sensing the object

A single current limiting resistor and a diode clamp to 5V is all that's required, or you could use a potential divider (two resistors), or as already suggested a current limiting resistor and a 5.1V zener diode.

 

[steev]

nice.
i need 5v output but with higher amp(need to drive 20 LED's ie might need 400ma current).so can u suggest me some good chip(MAXIM will be great as i can order some samples)

 

[akg]

Hi, stupid question (lol, one of these days maybe I will be electronically inclined enough to ANSWER the stupid questions rather than contributing ): A proximity sensor I am using is switching 24V. The controller I am using can only handle 5V ttl signals... So I just need a simple device to step from 24V to 5V.

Thanks!

i'd recommend a zener with a current limit resistor , or using a resistive potential divider

 

[gmanspwa]

A simple resistive voltage divider circuit. Two resistors one on top and one on the bottom. Tap output between them. Don't have a calculator but a 3K bottom and a 12K top should give you around 5 volts. Try this equation for more accuracy. and look up some similar schematics as it is hard to explain in text. 5Vout= R1(bottom closest to common)/R1+R2*24Vin. Maybe this will help if you have no IC's around didn't read you current needs use ohms law and use smaller resistors. Diodes work well too as they are almost perfect voltage regulators. Many options to do this work. Play around it's the fun of all this. Or use a 24V relay to isolate to your 5v Circuit. I hate doing that but I use PLCs and have to. I could be more help with a little more information. OP on this forum seem to be on different pages. Give us as much info as you can.

 

[sandhu]

sir i have a variable power circuit which has range 1.2 to 37 voltage but i require variable power supply in range of 5 to 15 **broken link removed**voltage . also i require it's PCB board circuit`

 

[Hero999]

Dear Sir,

Please do not try to hijack someone else's thread by making an off-topic post, it is very rude.

Regards,
Hero999