BS2 Power Draw

VANITY

How much total current does the BS2 consume?

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I initially thought that it only consumed 3 mA during RUN mode and .5 during SLEEP, however upon testing my circuit (prototyping on a BS2 HW board) i found it was sucking up 90 mA in SLEEP mode with NO pins connected. I then took everything off the circuit and ran this simple program:

DO
PAUSE 500
SLEEP 2
PAUSE 500
LOOP

I put some resistance upstream of the board and took of the serial port to finally get the current just barely above 50 mA (in sleep/ 53 mA running).

This is probably the sink current, but why isn't this current including in the Current Requirements ( says it =3mA)?

Is there any way to get this current lower? Could a pin be fried into place?


Minimal power draw is way critical for what I'm doing and any help would be much appreciated!

Mike Green

The BS2 is designed to draw only 7mA when running from a 5V supply (exclusive of anything connected to it - like an LED). The voltage regulator on the HW Board will draw an additional 15mA quiescent current. 90mA does seem a bit much and 50mA is still more than expected if true.

Your simple test program spends most of its time running at full speed (in the PAUSEs). The more time your program can spend in SLEEP or NAP mode the better (for power consumption). It's also helpful to set all the I/O pins you're not using to either HIGH or LOW or to use pulldown or pullup resistors (10K) on unused input pins. This avoids having them float which increases their power consumption.

VANITY

Mike Green,

Thanks for the tips, presetting all the pins cut down a few mA. I got the HW board down to roughly 35 mA at 3.7 V and 70 at 5 V. I realized the 50 mA from my previous post was at 3.7 V so I definitely won't be running it at that.

It has to be the HW board, I've put this thing through a lot in the past.

Any how I'm using an external timer chip so I'm thinking about just amping up the timer chip output and then having it switch a relay. This pretty much solves the whole problem of power because I'll only be using the board for a few seconds every 5 minutes and a few hundred mA for a few seconds won't consume much energy. I got all my other externals on latch relays so I'm not really running anything through the board anyways.

Do you think I might have any long term problems with the board after being disconnected from power for many cycles?

Mike Green

You're not going to have any problem with turning the HW Board on and off or being left off for long periods of time. Do be careful about powering up other things attached to the HW Board while the HW Board is off. The HW Board is not designed to handle that although the built-in 220 Ohm series resistors on the I/O pins will help somewhat with that.

You might want to look at www.emesystems.com. There's a link at the bottom of the page ("app-notes") to a lot of good information about Stamps and their use including a discussion of power consumption.