I am trying to feed the Arduino board from a large 1F capacitor for several seconds after turning off the board, but I have some problems.
The first time it works very well if I turn on the Arduino nano 3.3V with a small battery, it is on for several seconds but in the following steps it doesn't work, it doesn't start when i power it with the small battery. If I discharge the 1F capacitor and plug in the battery again, it works fine when I turn it off, it stays on a few seconds. From the first time I try to operate after switching off it does not work, nor does it turn on.
Summarizing:
Small 1 lipo battery with a 1F capacitor, arduino nano 3.3V
I turn on and off, the arduino stays a few seconds on. I repeat the process within a few seconds or minutes, it no longer turns on.
If I try the next day it works fine the first time but not the second time.
I have tried with many arduinos and also bluetooth modules but the same problem.
So you're discharging the capacitor and the system won't work until it has charged back up again. That seems fairly reasonable. It sounds like the discharged cap is shorting out the battery. How exactly are the battery and capacitor connected to the Arduino?
I am discharging the capacitor with the battery disconnected, and after it it works (stay on for few seconds), after discharging the capacitor it works fine the first time.
I am discharging the capacitor with the battery disconnected, after this, I mean that I connect the battery and disconnect the battery, it stays a few seconds on.If i plug the battery again it does not work (arduino does not power on)
Then, I short-circuit the capacity with the battery disconnected, plug the battery and the led lights come on, disconnecting the battery it stays alive for a few seconds. Plug the battery again, it does not work.
jtxu77:
Then, I short-circuit the capacity with the battery disconnected, plug the battery and the led lights come on, disconnecting the battery it stays alive for a few seconds. Plug the battery again, it does not work.
Sorry that doesn't make any sense. If you short circuit the capacitor you completely discharge it. So there's no way it can run the Arduino for a few seconds.
From what you say the capacitor is being charged from the small battery. So once it's run the Arduino for those few seconds it's empty (voltage close to zero). When you plug the battery back in it's voltage is dragged right down as it tries to charge the capacitor back up.
That's why I ask EXACTLY how everything is connected.
And you're still not saying where the battery and capacitor are connected to. And what is charging the capacitor.
Basically I don't believe you unless you mean something unusual by "short circuit". When you short circuit a capacitor (connect the two terminals together) you discharge it completely. It has no energy left. It can't possible run an Arduino.
Are you following the 1F capacitor's manufacturer's rules for charging the capacitor? Your description seems to indicate otherwise. If so, you may have killed the capacitor.
The Arduino running on the cap alone will run the voltage down to the point where the processor can no longer function. A single transistor fails to switch properly and it locks up the processor with no valid code to run.
But the cap is not fully discharged at that point. It is still holding that tail-end-charlie transistor in its "stuck" state. If you luckily stopped in a relatively low-power state then it could take a very long time to completely discharge the cap from there.
What happens if you connect the battery and then hit "reset" pn the Arduino? Does it un-stick?
The core processor of the Arduino is intended to run with this kind of unstable power. It has a "brownout detector" which is supposed to restart cleaner when the power comes back. It should be enabled by default. But it may be something else on the Arduino board which is having problems.
I think you need to re think your problem and do a bit of research on the amount of energy you will need then how much capacitance you need to support it. Ever consider how much energy the Bluetooth modules take.
Try this calculator: Capacitor charge and discharge calculator | MustCalculate This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil