How to ensure you have enough power to complete a task

Hi

I hope this makes sense.

Lets say I have a circuit connected to a battery. I want to transfer and hold enough power, before the battery is disconnected, to be able to start my Arduino, turn on a 6V DC motor ( .75a) for 1 second, then wait for 5 seconds and reverse the motor for 1 second.

I was thinking that a capacitor would do the trick, but not sure if that is the best way to do it.

My main concern is cost and size, I did think of having a rechargeable coin cell (if there is such a thing ) but again not sure how long the charging would take, etc.

I am hoping for no more than 1 sec to transfer the power before disconnecting the batter.

Any advice would be great

UPDATE: The device will be in a pipe and not accessible. The battery will actually be charge points which the device will float past.(during which that charge is transfered). The device will the continue flowing down the pipe until a set interval before starting its functions.

Why not just use the battery?

Its complicated...

The design has several nodes some provide power other do the work.

The worker needs to be as light and compact as possible due to confined space.

Hope that helps

Hand waving and vagueness is a good way to get the help to dry up around here. Why don't you just be specific about what it is?

No, that doesn't help, and it makes no sense to "transfer energy from a battery to storage, turn the battery off, and immediately use the storage", if I have understood your idea correctly.

A capacitor would have to be very large to power a 6V 0.75 A motor, even briefly. Coin cells are for tiny, very low power circuits.

Sorry did not mean to confuse so tried to limit the question to the details I needed help with.

If you are interest, the product ( or idea ) is to monitor valves within a pipe line.

If you want more please let me know...

PS. Thanks for at least looking at the question. :wink:

My problem with coil cells was I did not think they can be recharged. Is that not the case. I am limited to a case holding the device which is approx. 50mmx50mmx50mm. I was hoping for a small solution.

There are indeed rechargeable coin cells.

Have you tried looking here?

Yes there are rechargeable coin cells chargers ( first link after I typed it in google... wow ) the problem is the chargers.

How would I charge the coin cells within my device (floating in the pipe ) when the charger is outside the pipe.

If I could get a charger to fit in my 5x5x5cm space ( not including the other parts ) I would have the problem of powering it ( as most seem to be AC powered ). So if you know of a DC version which fits please let me know, but I have a feeling it will pricey, but then again maybe that may be the cheapest solution.

I know I ask silly questions but please try and not make too much fun of me. I am trying in my own way to get enlightened.

Thank you for the idea.

keshman:
How would I charge the coin cells within my device (floating in the pipe ) when the charger is outside the pipe.

this is the first you are mentioning the thing being inside a pipe. Can you not see how a detail like that might be important?

Why don't you drop the vague answers and just come on out with it?

I don't think anyone else should waste any time on this until you can give us some of the details about what we're building.

Sorry.

I had updated my question when you first asked for more information. As I said I was not trying to be vague but keep the question simple.

After looking at your suggestion of coin cells, it looks like I may be able to use a charger using an ic ( meaning I can use received DC power to run the charger ) but not sure how many mAh batter would be needed or time it would take to charge. In my case I only at a second at most to charge the device as it passes down the pipe.

If I am not being too vague I would appreciate any info on the above questions.

Thanks again for at least looking at my question.

keshman:
Sorry.

I had updated my question when you first asked for more information.

Don't do that. Just post a new post. I'm not going to go back through looking to see what might have changed.

keshman:
As I said I was not trying to be vague but keep the question simple.

Yes, but you may have oversimplified. You cut out all the details that could help anyone give any sort of intelligent answer.

keshman:
After looking at your suggestion of coin cells, it looks like I may be able to use a charger using an ic ( meaning I can use received DC power to run the charger ) but not sure how many mAh batter would be needed or time it would take to charge. In my case I only at a second at most to charge the device as it passes down the pipe.

yes and until you come on out with the details, you're on your own figuring that out. How could anyone here tell you without knowing the first thing about what it is that you want to build?

keshman:
If I am not being too vague I would appreciate any info on the above questions.

So far you've told us that it is 5cm x 5cm x 5cm and that it goes into a pipe of some sort. Do you really think that is enough information to figure out what you need? I guess you can wait until someone who can read your mind comes along.

keshman:
How would I charge the coin cells within my device (floating in the pipe ) when the charger is outside the pipe.

How about the same way you planned on charging your battery-free device before:

keshman:
charge points which the device will float past.(during which that charge is transfered).

But there's a much, much simpler way: charge your device before it goes into the pipe! Just make sure it has enough power on it to do its job(s) whatever that may be.

A 5x5x5cm cube which also has to hold this 750 mA motor won't leave much space for electronics or anything else... (after deducting the wall thickness you're down to 4.5x4.5x4.5 cm at best).

I think somewhere in that waffle you said your power source needed to be charged in one second. I assume you mean fully charged from empty.

If that's really needed then you are pursuing an impossible project and might as well give up now. There are currently no rechargeable cells, coin or other, that can be charged anywhere near that fast. Not even a high value capacitor can safely be charged quite that fast though they can be "charged" a lot faster than batteries.

A more practical choice may be to make your device so it can do multiple passes through your pipe without needing to be recharged and then take it out of service for some sensible amount of time (at least several minutes) to recharge it.

Steve