monitor voltage input

kirtm · 24th March 2009, 04:16 PM

I have been tasked to design a piece of test equipment to test an Lm338 circuit used as a current limiter. I would like to monitor (LED?) a variable input supply (+4 to +20VDC) (2.0A) through a switch that would supply the LM338 circuit. Something that would show that power was supplied to the circuit. Any suggestions? Thanks.

Fuzzymuff · 10th April 2009, 04:28 PM

http://sound.westhost.com/project60.htm

AndrewT · 10th April 2009, 05:55 PM

Hi,
a LED with a couple of series diodes and a resistor (3k) will do that.
The 1.6V LED (red) + 1.4V (two diodes) will be off @ <=3V.
At maximum voltage it will be very bright. At minimum voltage it will be very dim.

You could replace the two diodes with a two terminal CCS. Buy a 5mA CCS it will show constant brightness >=6V and dim as 4V approaches.

24th March 2009, 04:16 PM	#1
kirtm diyAudio Member Join Date: Mar 2009	monitor voltage input I have been tasked to design a piece of test equipment to test an Lm338 circuit used as a current limiter. I would like to monitor (LED?) a variable input supply (+4 to +20VDC) (2.0A) through a switch that would supply the LM338 circuit. Something that would show that power was supplied to the circuit. Any suggestions? Thanks.

10th April 2009, 04:28 PM	#2
Fuzzymuff diyAudio Member Join Date: Mar 2009	c here http://sound.westhost.com/project60.htm __________________ Wrap it in foil, and plug it in.

10th April 2009, 05:55 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, a LED with a couple of series diodes and a resistor (3k) will do that. The 1.6V LED (red) + 1.4V (two diodes) will be off @ <=3V. At maximum voltage it will be very bright. At minimum voltage it will be very dim. You could replace the two diodes with a two terminal CCS. Buy a 5mA CCS it will show constant brightness >=6V and dim as 4V approaches. __________________ regards Andrew T.

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