BS2 Homework board 5V Regulator

Dr.No

I'm now using an external power supply.
It seems it best not to power more than 2 relays (5V) in parallel.

Yes, it working great right now... but I'm up to 12 relays!

Post Edited (Dr.No) : 4/11/2008 4:11:41 PM GMT

PJAllen

If you're going to tie into·an "on-board" source, a regulator's voltage source should be the BoE/HWB "Vin" (which is the battery + or the external supply +V), definitely not "Vdd".

Adding another regulator won't enable you to draw extra (more than·recommended, absolute maximum)·current from an I/O pin.

What are you trying to do?

Dr.No

I need to power 5 relays (5V 20mA x5 = 100mA). I was hoping to use Vdd to relay to Vss
and avoid the limitations of the pins.

The stamp is hook up to a 1A 9V power source.

PJAllen

OK.· In any event, for as many relays as you need to use, you will need to implement switching transistors (2N3904, PN2222, 2N2222, etc.)

If you are using an HWB, you will need an "external" regulator for a separate, higher-current 5V source (get a 7805, not a 78L05.).



If you have a BoE, the on-board regulator should be enough.· In that case, use Vdd for +5 instead of a regulator.· (Some may insist or otherwise suggest that you use a separate 5V source altogether.)

Post Edit:· I was reading your previous exchange on this very Subject -- http://forums.parallax.com/showthread.php?p=720414·and I'm somewhat concerned.
Are they 5V coils or 12V coils or what?
What are the ratings printed on these relays that you intend to use?

Post Edited (PJ Allen) : 4/11/2008 1:21:21 AM GMT

Dr.No

I'm now using an external power supply to directly power the relay switches and relays.
And everything works great... right now I'm burning in the project to see
how well it works. I'm up to 12 relays from 4. There were problems that
arose that just needed a relay to fix the problem.