Power Supply Question

Perhaps someone with more electronics experience than myself can give me an idea of roughly what sort of power supply I need for the following scenario:

I am looking to power:

11 PIC16F690 microcontrollers which run on +5V 1 cold cathode light which runs on +12V (these are the specs given: Input voltage of inverter: 12v, Output voltage of inverter: 680v, Current draw: 5.0mAv)

1 +3.3V accelerometer

10 16x2 character LCD displays which run on +5V Also, the PIC will be sourcing 11 relatively standard LEDS (4V voltage drop @ 20mA)

I have a 3.3V, 5V, and 12V voltage regulator circuit built, and I'm wondering if I'm going to be able to just buy a wall wart with enough voltage/current output to just run it to all three of those voltage regulators in parallel, and then have those power the appropriate devices.

Is this plausible, or am I going to need some more heavy duty type of power source? If I could do it with a wall wart, what approximately would I want my voltage/current output to be for those items?

Best, Mike

This is pretty easy. You need to get the basic current data from the data sheets for each part (max, not typical), multiply by the number of units you are using and add together the current for each supply voltage. Be careful about directly sourcing current to that many LEDs from the PIC. There is often a max spec for the total current passed through I/O pins and 11 LEDs may just exceed this.

The CCL draws what it draws. If the data sheet says it draws 5 mA at

12 volts, then that is what it needs. If it is using 5 mA at 680 volts, you need to read the data sheet for the power supply to see what the PSU draws when the load draws 5 mA.

You will need to read the data sheets for all of the other parts. The accelerometer may draw a significant amount of current, I don't know much about them. The LCDs should draw little current.

Once you know how much current you need from each supply, you can figure how much current they will need on their inputs. Switching supplies will draw as much power on the input as is going out the output with a factor for the efficiency. Linear supplies draw the same current on the input as on the output, with a little extra to power the regulator (read the data sheet for the quiescent current).

Just multiplication and addition. :^)

Rick