Power misunderstanding?

Good afternoon,

I own a ORIGINAL ESPRUINO, which I connected to a SRD-05VDC-SL-C relay (http://rabbitmax.com/files/SONGLE-SRD-05VDC-SL-C.pdf) using the following pin mapping :

C6 <--> IN
GND <--> GND
VCC <--> BAT

When I connect this to my computer using micro-USB plug, the relay works perfectly (red light when powered, green light when active, and I hear a little 'click' sound when activating and deactivating).

Then I tried to power the Espruino using a 2 x coin cell battery holder (https://www.adafruit.com/products/783) which seemed to me more than enough (2 x 3V batteries so more than 5V). The red light on the relay does switch on, but it's more faint ; but the green lignt is hardly visible when the relay is supposed to activate, and I can't hear any 'click' sound any more, making me suspect that the relay can not draw enough power to act as supposed.

Can anyone here please direct me to solve this?

Thanks !

Not much a surprise here: the cells have a 225mAh capacity, which roughly says: you can pull 22.5mA at nominal voltage - 2x3V when serial - for about 10 hours before the voltage drops below usable... Your relay - according to datasheet - is guzzling about 90mA... which is four times what the cells can push with keeping up the nominal voltage...

Running relays in a battery driven world is a challenge... I do not know what you want to switch in the end, but if you driver to switch that is that draining, it's going not for a 'long' time...

How often for how long over what time should the relays be on? You have to look for an alternative... If you still think you need a relays, you could think of a bistable relays that sucks not more than 20mA. Since such a relays needs only a pulse to change state, a capacitor can help to support the spike in current consummation.

As @allObjects says, it'll be the amount of power you can draw from coin cells. To be honest sometimes they can even struggle to power an Espruino board (when it isn't sleeping) let alone a relay as well.

You could look at using 4 AA cells - while a bit bigger, they'll last for years with deep sleep enabled, and will easily provide enough power for the relay.

Thanks for your swift replies. I'll give the 4 AA configuration a try before switching to a USB powerbank.

My need is quite simple: I need to short a circuit three times per hour, during 3 seconds each time. The functional need is to simulate the press of a button on my doorbell at given times - what the physical button actually does can be simulated by placing a wire between two pins. I succeeded in doing this with the aforementioned setup powered by USB...

Thanks a lot

@user57476, your door bell, is it one where you switch the actual power? ...and how much is the door bell drawing, if so?

If it is the old type of door bell where you just power the bell for the time duration of the ring, you may even get away with super cap which your charge with 'parasitic power' over a diode(s) and a resistor. If the the super cap does not make it, a small, rechargeable power pack from cordless phone set could do to. The parasitic power has just to deliver enough voltage...

Multiple diodes may be needed when the door bell power is alternate current, which for the 'old' doorbells it is.

If it is a newer door bell, it is a different story...