Hello. As I am more of a programmer than an electronics guy, so I am stuck and in need of some help in a current project.
I have a 24VDC power supply. I need to tap off 0 to 5 VDC (via a potentiometer) to power aproximately 200ma (6 separate 0-5vdc 30ma circuits in parallel to be more exact). From what I have read, a simple voltage divider won't work because of the current requirements. The 200ma does not need to come off an arduino pin or anything, just from a separate power supply.
Can somebody point me in the right direction?
thanks
It is so rare to see the word "power" used correctly that I think I misread your post initially.
Do you want ONLY 5v, i.e. you don't need 1 volt, 2 volts, etc?
If so, I presume you meant that the current the source had to deliver varies from time to time?
If this is your requirement, your life will be simple. There are things called "voltage regulators" out there... a previous poster has already pointed you to one, but the one he cited is capable of delivering more than just 5v.
Yes... I saw the "0-" part of the OP, and yes, that does suggest that the poster may need the different voltages between zero and 5... just hoping that things were... for once.. simple!
jondecker76,
if I understand the goals correctly ...
The LM317 variable voltage regulator is not suitable because the output voltage is selected by its fixed external resisters, whereas the desired output voltage is a variable "0 to 5V DC".
I suggest connecting a 0 to 5V DC analogue output from the Arduino to the input of 6 op-amps with unity gain (so their output is 0..5V DC).
Choose op-amps like the National LM6172 which can supply Output Current 50mA/channel. It comes in a 8-Pin DIP package (ie. it looks like a typical IC seen on circuit boards). Being dual channel, you would need 3 x LM6172. Its maximum rated Supply Voltage (V+ [ch8722] V[ch8722]) is 36V so you should be able to connect it to your 24V supply.
The LM317 variable voltage regulator is not suitable because the output voltage is selected by its fixed external resisters, whereas the desired output voltage is a variable "0 to 5V DC".
A quick look at the datasheet shows that the fixed resistors can include a variable one! The real problem with the 317 is that it doesn't go below 1.2V in the standard configuration.
The 'standard' solution to this problem is to use a potentiometer to set the voltage and an op-amp driving a series-pass transistor or darlington - the op-amp needs to go down to the negative rail and handle the 24V supply but otherwise isn't very critical.
The circuit at the end of Voltage regulator - Wikipedia is the sort of thing, but you replace the zener with a potentiometer (and given the voltages involved you can simplify it by connecting the op-amp inverting input directly to the output.
Variable voltage regulator are not very efficient in this case... Using such IC will lead to a high power dissipation : 24-5 =19 volts x 0.2Amp= 3.8 Watts... welcome heatsinks...
May be using a DC-DC converter + voltage regulator ?
Gozaki