Apologies for the simplicity of my description, I'm a bit of an electronics hack, and while I can put together a circuit given a schematic, my ability to design with discrete compoments is non-existent. So to my problem...
I have a piece of equipment that is battery powered, and has a single on/off switch. Hold for 2 seconds and it powers on, hold for 2 seconds and it powers off.
I would like to power on/off this device based on existence/non existence of a external 5v power supply.
So, normally the device will be off, but when an external 5v source (basically USB VCC) is provided to a circuit, I would like to close a relay across the on/off switch, the relay has to be held for 2 seconds so that the device will power on. The device itself is 4.2 v internally powered by a li-ion battery, so I don't believe the relay would need to be very beefy (or perhaps there is a better way than a relay (an transistor ?)...
Now once this has happened the device will be operating and all will be good.
At some subsequent point the external 5v supply will be lost, and what I would like to do is to again pulse the on/off button for 2 seconds to switch off the device. The problem is without tapping into the power supply of the device itself. (I'm assuming that I would need to utilise a CAP of some form to hold enough charge to do this when the external power is removed.
Is there any neat way that I could do this without requiring a lot of bulky componentry that could effectively do this.
Apologies for the complete noob-ness of this request, I really don't know where to start.
I have a piece of equipment that is battery powered, and has a single on/off switch. Hold for 2 seconds and it powers on, hold for 2 seconds and it powers off.
I would like to power on/off this device based on existence/non existence of a external 5v power supply.
So, normally the device will be off, but when an external 5v source (basically USB VCC) is provided to a circuit, I would like to close a relay across the on/off switch, the relay has to be held for 2 seconds so that the device will power on. The device itself is 4.2 v internally powered by a li-ion battery, so I don't believe the relay would need to be very beefy (or perhaps there is a better way than a relay (an transistor ?)...
Now once this has happened the device will be operating and all will be good.
At some subsequent point the external 5v supply will be lost, and what I would like to do is to again pulse the on/off button for 2 seconds to switch off the device. The problem is without tapping into the power supply of the device itself. (I'm assuming that I would need to utilise a CAP of some form to hold enough charge to do this when the external power is removed.
Is there any neat way that I could do this without requiring a lot of bulky componentry that could effectively do this.
Apologies for the complete noob-ness of this request, I really don't know where to start.