View Full Version : Applying 9V on Vin, should VDD pin be 5V?

01-08-2006, 01:18 AM
Hello, I have a question regarding powering the BS2p,

i Read somewhere that if i don't have a steady 5V source, i can apply a 6V-12V on the Vin, and internal circuitry will regulate the voltage to 5V.

My question is:

If I apply a 9V voltage on the Vin pin (pin 24), and probe the VDD pin (pin 21) with a voltmeter should it read 5V ?

Simple question, I know, but it seems I can't get my stamp to work, i was wondering if it's busted.


Tracy Allen
01-08-2006, 01:26 AM
Yes. The voltage Vdd pin 21 should be 5V, with respect to Vss pin 23. Reset pin 22 will also read 5V.

Tracy Allen
www.emesystems.com (http://www.emesystems.com)

01-09-2006, 02:20 AM
Note that the voltage regulator on the BS2 is 'special', in that it can survive having +5 put IN to VDD, OR you can put 6 to 12 volts IN on Vin, and use Vdd as a +5 volt output.

But yes, when you drive Vin, the Vdd pin should go to +5 out (as compared with Vss, which should be ground).

Chris Savage
01-09-2006, 07:28 AM
Another thing to consider is that the on-board regulator can only supply about 43 mA of current, so it's not advised to use it for driving anything that would require that kind of current or more.

Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)