When taking care of electronics you requirement 1 crucial thing, electricity. For rather a while now if I needed 5 volts I would just get hold of my homebrew arduino, however that is not always helpful as well as its tethered to the PC as well as it does not have 3v. If I desired 3 volts, now I am digging around trying to find my UBW32 which does have 3v3 however now I have a 50$ microncontroller with extremely little regulators (so as a result only little loads) dangling around just for power, as well as its a mess.
So I requirement just a board that takes some DC from a wall wart as well as regulates it to usable voltages, as well as I set about to make it. This regulator board puts out +5, +3.3, variable as well as unfavorable variable voltages, is quite simple to make, as well as make a great addition to the bench. (until I can get a genuine bench supply someday)
Now I understand this is not ground breaking hackery, however I hope it assists somebody out there, join us after the break to see what’s going on.
First up, parts! I started by examining the datasheets for the 3 regulators, as well as quite much throwing a lot of of their recommendations away as a lot of of this was scavenged parts. Beggars can’t be choosers.
That works mainly okay, however because of my resistance options on the LM317T I am loosing a bit a lot more (about an additional volt!) than I must be in the regulator. I utilized 100 ohms as well as 1khoms for the voltage modification … 120 as well as 2k or 240 as well as 5k would have been a much much better choice, if I had those parts on hand.
But this is what I ended up using
1*SPST toggle switch
1*LED of your option as well as proper resistor for 5 volt operation
3*Silicon rectifier diodes (I am utilizing 1N4001’s however a lot of would do fine)
2*47uf capacitors with voltage scores higher than ~16 volts (I am utilizing 50 volt caps)
1*10uf capacitor (its for the 3.3 volt line so anything a lot more than 3v will work)
1*4.7uf capacitor (again I am utilizing a 50 volt)
6*100nf ceramic capacitors (code 104)
2*100 ohm resistors
1*1k ohm resistor
1*1k ohm trimpot
1*7805 in a TO220 package
1*3 volt regulator in a TO220 bundle (I am utilizing a ST “LD33V” though its not common)
1*LM317T in a TO220 package
1*555 timer
4*Dual terminal/ screw blocks
1*Large 3 setting heatsink or 3 typical TO220 heatsinks
Wire, solder, as well as a 2 setting jumper
More or less voltage is available in is filtered a bit with capacitors as well as is fed to the 7805 as well as 317T, the 3v3 regulator is wired to the output of the 7805 (along with the LED) so it does not have to decrease a lot of present as well as not run hot with very little loads. keeping in mind there are 2 regulators linked to a wall wart this thing in theory might suck as much as 2.5 amps out of your supply so you either requirement a wall wart that can manage it or be extremely mindful of exactly how much present you are drawing.
Next is the schematic .. not much to state right here its a schematic… (click for big version)
Update: fixed the backwards diode
Finally I have to make the thing, I select perf board with copper pads on one side, as well as uninsulated 22 gauge solid tinned copper as I discover this method to be quite simple as long as the design is not as well complicated.
Construction starts by installing the regulators to the warm sink. I got this warm sink as well as lots of of the capacitors out of an old dead PC power supply. It is quite huge as well as must do the technique just fine, however there is a catch. Each of the regulators installing tabs go to different functions, so unless I want to link the outputs of the 3v3 regulator as well as the LM317T to the ground of the 7805 I am going to requirement either separate warm sinks or some silicon pads as well as nylon washer isolation hardware which my power supply was gracious sufficient to provide. (only after I threw them away as well as had to dig in the garbage for 20 min)
Here is a shot of the power input as well as 7805 all wired up as well as checked working.
Another shot with the 3v3 regulator wired up as well as checked working.
Another shot with the 317T wired up as well as checked working.
And lastly the 555 voltage inverter is in location as well as working. While they make voltage inverters as well as I have a 5 volt one somewhere I rather like the concept of having one that can be hooked as much as the 317 since I truly don’t understand if I will requirement -12, or -5 or anything in between.
Keep in mind this is a kludgey method to make a unfavorable voltage, as well as it will not be balanced with the positive output of the 317 (you loose 0.7 volts or a lot more in the diodes). likewise it takes a few seconds before it stabilizes on a voltage, so begin low as well as stop a bit short as it will continue rising for a few seconds. You may be able to lessen that by utilizing a lower value capacitor onthe 555’s output, ideal now I am utilizing a 47uf however I have seen whatever from 10 to 470 depending upon which schematic your looking at.
Anyway right here is the final product as well as I am prepared to rock. You may notice a jumper block on there as well as that is to cut power going to the 317. With the losses because of my resistance option as well as the 555 timers output, that part of the circuit draws about 37ma, the 7805, led, as well as 3v3 regulator only draws 36ma (20 for the led). So if you’re not utilizing it why bother adding the extra tons to your power supply? I may go back as well as modify that.
Thanks for looking!