PWM for regulated power supply

Hi folks,

I plan to build a picaxe controlled power supply 0-30V and current limiting 0-3 amps
The picaxe will have to deliver 2 separate dc voltages (1 for voltage, one for current) Is this possible? I get a bit confused but learned a resolution of 1024 is possible.
Voltage regulation (about 30 V max) will have a resolution of about 0.03 Volts
The other pwm doesn't need such fine resolution but 1024 steps will result in about 3 milli Amps per step

Altenatively I could use i2c D/A converters of course...

Schematics are not available yet but it will be loosely inspired by the http://www.eevblog.com/usupply

Bottom line: I need 2 seperate PWMS, 0-1024 that may share their clock but further not influence eachother.

Further, there will be about 8 buttons and 1 LCD needed for the project

Tnx,

Erik

That should be perfectly possible.
The PWMout function can work to 10 bit resolution (1024 steps).
If you feed it into an RC network you will get a smooth DC voltage. (between 0v and close to PICAXE supply voltage)
How you convert those voltages into PSU voltage & current will be the challenge!

On some Picaxe parts can't you only have one PWM output and not multiple PWM outputs?

14M2 has 4 PWMOUTs I recall...[and 20M2]

BeanieBots said:

That should be perfectly possible.
The PWMout function can work to 10 bit resolution (1024 steps).
If you feed it into an RC network you will get a smooth DC voltage. (between 0v and close to PICAXE supply voltage)
How you convert those voltages into PSU voltage & current will be the challenge!

Click to expand...

You might like to look at this thread starting at post #22

http://www.picaxeforum.co.uk/showthread.php?10039-picaxe-controlled-variable-power-supply

I plan to let the picaxe deliver an adjustable output of 0-5 volts (indeed, a pwm and rc network)
Then this voltage will be fed into an opamp with a gain of 6. This opamp then delivers an adjustable 0-30 v

This voltage will be delivered at the reference of a stabiliser instead of the resistors that are usually there. Any regulator will work but the 7805 will then deliver 5V as the reference is normally connected to gnd. if this input is fed with 5 V, the output will be 10 volts. If connected to 30 Volts, the output will be 35 volts

In the eevblog article they use a regulator that is adjustable from 0 volts. The output will be sligtly off the reference but this is a constant and can be corrected in software.

I still have to draw my own design but will do later on.

Remarkable property of a design like this is the maximum current can be set (and shown on display) without any load!

I'll keep you posted but it will take a while because the eevblog part seems not available in local stores here in the Netherlands