what is the useable voltage of the output pins of an 08M?

[hokieed]

I understand that 20mA is available to each pin, but what should the voltage be? I assume there is 4.5 volts, since that is my power supply, but is there a drop through the picaxe?

I know this is a pretty simple question, but all my looking didn't provide results. (I'm a very green newbie) Thanks

 

[BeanieBots]

Be careful, you can have 20mA from any pin but you cannot have 20mA from all of them at the same time.
The off-load voltage will be just a little down from whatever your power supply is. It will start to fall quite rapidly when you start to load at currents approaching 20mA.

Why do you need to know this? What is your concern?

 

[womai]

The output voltage is heavily dependent on your load conditions. See also the recent thread <A href='http://www.rev-ed.co.uk/picaxe/forum/topic.asp?topic_id=6740&amp;forum_id=30&amp;Topic_Title=Input+and+output+impedances&amp;forum_title=PICAXE+Forum&amp;M=True&amp;S=True' Target=_Blank>External Web Link</a>

According to my estimate there the Picaxe drive impedance is most likely somewhere around 200 Ohms or less. If you drive a high impedance load (e.g. the CMOS input of another Picaxe or some 74xx digital gate), then the output voltage will be very close to your supply voltage (4.5V in your case).

Wolfgang


Edited by - womai on 26/04/2007 08:04:00

 

[hokieed]

Thanks for the info.

In short, I am trying to fade out an array of LEDS using the PWM output. I can get it to work great with one LED, but I had to ask about loading up the other pins first. It appears it will not work.

I'll post a new message today detailing the specifics. (with circuit diagrams and the code) Maybe I can get some good advice here. So, far, this forum has been great! Thanks for the replys.

In short, I am

 

[Michael 2727]

Try using a 2N7000 MOSFET via a 2K2 resistor, they are good for 200mA.
Or many BJTs will work also.

Read picaxe_manual3.pdf, interfacing etc.