Voltage Regulator





Introduction: Voltage Regulator

IMPORTANT I have recently dug this out of a box and tried to regulate 9v from an RC car battery, it did work, but then there was a puff of smoke and it became extremely hot. This may be because i have previously fried the regulator, but i thought i would let you all know so you can be careful. I may need some filtering capacitors, not sure. please tell me if you have any ideas.

This is the circuit for converting a 12V car supply to 4.5V. 

You will need:
2 X 2 wire PCB mounted terminal blocks (optional) 
1 X diode
1 X L78S05CV voltage regulator chip 
Some verro board
Some Wire

Step 1: Connect the Terminal Blocks

Drill a hole to break the tracks and solder the two terminal blocks as shown in the picture. 

Step 2: Connect the Wire Jumps

 Solder the jump wires in. 

Step 3: Connect the Diode

 Solder the diode in over the break in the tracks. 

Step 4: Solder in the Voltage Regulator

 Solder the voltage regulator in (bend it down so it's flat if space is an issue). 

Step 5: Test

 Connect the power into the input end of the board. Test between the connections at the other end and it should read the voltage the chip is set for. 



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you forgot the decoupling capacitors. this may have had something to do with your (puff of smoke)

any one between 10uf and 100uf will do the trick.

what value of diode ?

You mean for a .6V drop -- pretty much any silicon diode. Just get one rated for the voltage (not generally and issue). Put it in in the correct polarity and the output will be about .6 lower than the input. Just the nature of the semiconductor...

I'm not entirely sure, i didn't check! It needs to be able to withstand 5/6 V, i just used whatever i could find in the school tech lab. It's only purpose is to protect the circuit a bit, so it isn't actually needed. It also has the effect of lowering the voltage by 0.7V, which leaves 4.5V, so is perfect for a picaxe chip.

My car ends up with a host of connections at various voltages and power requirements from 5v to 12. Phone. USB, GPS... No current regulation (fuse notwithstanding) is needed.

Short of duplicating the regulator for each output voltage, how might I deliver multiple voltages in this basic format?

Errrm. I'm not certain. You could try variable resistors to chage the voltage, but otherwise, i'm not much help.


@AntMan thanks for your reply. I did spot another Instructable that both used separate regulators for separate voltages and used multiple regulator chips of the same voltage (parallel outputs) to increase the current ratings. I didn't realize you could do that. I think resistors (in series) would work well only in the case of device require constant current; there's also the heat dissipation. I could also use diodes in series for .6v/diode drop that'd be current-independent.

Thanks again for both the "instructable" and the ideas!

i would use a regulator for 9v and 5v and then resist it down to the odd voltages.. i use mini blade fuses they fit on pcb well.

Come on guys!  This is a simple regulator, almost self-explanatory and should work quite well for simple purposes.  Stop bugging the author!!!

Now for some suggestions:  a couple of capacitors (one across the input lines, one across the output lines) should reduce noise, if that is a problem...  Please also note that this is not very strictly regulated (due to the variation of the voltage of the diode with current), but it should still work quite well for most applications (heck! it would still work quite well if you feed 5V to something expecting 4.5V, but don't blame me if it does not work, makes your device blow up in flames and takes the car with it...).