BS2p40

ErikdS

Hello,
it's very nice to have a microcontroller with such a huge number of I/O pins, but I'm getting worried I cannot power all the peripheral devices my µcontroller is hooked up to from the single V supply pin on the BS2p40. So I'm not talking about drawing current from the I/O pins but from the 5V pin: how much current can I draw from there (assuming I powering the µcontroller through a 9V battery.
Thx for your attention!
Erik

erco

Simplest (not best, efficiency-wise) would be to add a simple LM7805 regulator to power your peripherals. A 9V battery won't last long, though. Five AA batteries would last a while.

Mike Green

Theoretically, the voltage regulator on the BS2p40 module can supply up to 150mA. In practice, this is limited by the amount of heat that can be dissipated which depends partly on the voltage drop across the regulator. A 9V battery is a poor choice for that since the power dissipated = (<supply voltage> - 5V) x <current drawn> = 4V x <current drawn>. You'd do much better with a 6V or 7.2V-7.5V battery pack. You'd also have better results using an external voltage regulator that supplies +5V to the Vdd pin of the BS2p40 (and your other stuff). A switching regulator would be the most efficient and produce the least heat at higher input voltages. One such ready-made switching regulator is this one. Note that you'll need more than 6V for either the LM7805 or the switching regulator mentioned.

Duane Degn

I have several of the regulators Mike mentioned, but my new favorite are these inexpensive ones on ebay. They are adjustable so you need to use a voltmeter to adjust them to the proper output voltage.

erco

Thanks, DD! 4 ordered, best $7 I've spent today.

But the $2 tall boy I bought after a hard 30-mile bike ride was a close second!

This is still a good deal for under $7: http://www.ebay.com/itm/310574419959