variable 0-5 volt milliamp input to a high amperage variable 0-5 vdc output

Thread Starter

BobW55

Joined Jul 22, 2008
46
I am building a laser engraver, the current setup uses a 12vdc buck to drop to 5 vdc @ about 6 amps.
It uses a IRFZ44n to switch on/off the 12 vdc input to the buck.
I want to use a variable input 0-5vdc I am sure only a few milliamps, to be able to vary the laser power by varying the buck 5 vdc output
I have been searching like crazy but not finding anything premade that I am aware of.
Can you suggest anything ready made, or suggest where i might go to read up about building my own.
 
Last edited:

ElectricSpidey

Joined Dec 2, 2017
1,070
Sounds like something you could do with a pot (voltage divider) and a power transistor configured as common collector. If your 0-5 volts is coming from some signal source, you can add an Op-Amp

The wasted wattage wouldn’t be too bad, probably about 8 watts or so when set at half power.

You would lose about .7 volts or so on the output…

As far as keeping the output purely from the buck, and getting a variable output…well that’s a little above my pay grade on an online forum, but I’m sure somebody with more experience with that sort of thing can help.
 

Thread Starter

BobW55

Joined Jul 22, 2008
46
The current set up uses the IRFZ44n as a on/off switch to the 12 volt input to the buck. The buck has a pot to set the output voltage and current.
Right now I can only vary the time the laser is on/off (PWM) via a variable 0-5vdc from the controller (Spark Concepts CNC ver4)
when the board with the IRFZ44N sees about 0.6 volts it turns on. There is a small opto isolator board with a 12 vdc input that the IRFZ44N is mounted on.
I thought about adding an external resistor to the voltage control pot on the buck, but when you start adding voltage, the output of the buck drops. I want it to increase. Yea I could use an inverter on that input. I just thought maybe someone knew of a ready made buck that has an external voltage control.
That one you linked to is similar to what I have, but the TTL/PWM control is built into it.
I'm still searching.
 

Thread Starter

BobW55

Joined Jul 22, 2008
46
I have no PWM output from the controller. It varies the output from 0-5 volts, (0%= 0 volts 100%=5 volts) I need that to vary the voltage to the laser from about 3.5 to 5 volts max. @ 4 amps ( 10 watt laser @ 5 volts about 2 amps but I like overhead)
May have to use a microprocessor (PIC) and just make a PWM output
 
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