pwm to voltage

[computer]

hi,

just wondering if I can smooth out the PWM signal from a 5v pic output pin to create a stable 0-10v voltage for powering a disco light controller.

someone told me a simple capacitor, chargepump and resistor would do but I'm not sure how to and what to connect up?

any help?

 

[Nigel Goodwin]

hi,

just wondering if I can smooth out the PWM signal from a 5v pic output pin to create a stable 0-10v voltage for powering a disco light controller.

someone told me a simple capacitor, chargepump and resistor would do but I'm not sure how to and what to connect up?

any help?

Just a resistor and capacitor, a simple low pass filter - you can download an application note from MicroChip which shows you how to do it.

 

[computer]

so am I looking at the thing on the top of page 2 in: https://www.electro-tech-online.com/custompdfs/2004/05/00538c.pdf

where can I get that opamp?

 

[Oznog]

The lowpass filter alone will only give 0 to 5V though, not 0 to 10.

The charge pump is remotely possible, but it's complicated and there are several problems you may not be able to fix.

First off, how much current does the disco light controller require? If it's more than a milliamp or so, you must buffer the signal since the resistance of the charge pump and lowpass filter is too high. If you're doing that, just use an op amp. You can use a charge pump to get a +10V supply out of +5V if you don't otherwise have a higher voltage available. Still, your op amp probably won't drive this close to the rail.

Second, is the signal grounded at the same point as the PIC will be?

Third, does the signal need to be analog, or can it actually use a PWM straight out? Lights can usually be controlled better with PWM sources than analog voltages.

 

[crust]

Most of these lighting decks need a 0-10V analog signal. Usually the device than does the PWM for the lights. They do not use much current, but my experience has been buffering the signal seems to work reliably with more cable/light combinations.

 

[Nigel Goodwin]

The lowpass filter alone will only give 0 to 5V though, not 0 to 10.

Sorry about that, I didn't notice it said 0-10V, you simply need to use an opamp to buffer and amplify the output from the filter.

 

[computer]

heh,

the controller needs only a few ma iirc, and there are 4 channels. the device needs 0-10v input analogue.

needs some circuit diags here as I'm not too sure. some part details would be nice too (ie part no.)