Power down external devices

Hi

As I am planning to have Espruino powered entirely by solar panels and batteries I would like to know if there is any way to power down external devices such as the cc3000 or a 433mhz radio transmitter when not in use in order to save batteries.

As devices is powered by vbat or 3.3v could there be a kind of switch on/off function for those pin headers? What will happen when Espruino goes into deepsleep mode? How will that affect the powering of external devices?

Thanks again

There is no builtin switch on the Espruino board. You could switch the parts on and off with MOSFETs though (SOT23 MOSFETs can be soldered into the prototyping area).

In the case of the CC3k, the VBEN pin might let you turn it off. Not sure whether it's just for resetting the part, or whether it actually turns it off.

When Espruino goes into deepsleep, if there are attached devices, they will continue sucking power at whatever rate they normally do when not told to do anything else. Deepsleep does not turn off power to any of the power pins.

It might be worth measuring the current draw of the 433Mhz transmitter - I think it is probably very low when it isn't transmitting, so you may not have to worry about disconnecting it.

VBEN on the CC3000 is controlled by the Espruino already, and it does power down the CC3000 module. However because the module itself contains a voltage regulator that isn't powered down, the module will always draw around 4mA (unless disconnected somehow).

FETs could be a good idea for the disconnection - see this page for more info. You could even use a Relay module instead if you want an easy solution. They will draw a bit of power when they're on - but if they are off for most of the time then it'd be fine.