Capacitor Problems
From what I can find online, I want a capacitor with at least half of the voltage higher than the battery voltage (so >16v). I have yet to find a page that discusses how to determine what / farad value capacitor to get. I'm trying to use a capacitor to 'smooth' the current, a suggestion from a friend when my arduino shuts off from a voltage drop.Twice I've bought a 35v capacitor (10uf and 100uf). Both times I solder it into the positive lead coming from the pop-on-cap to the 9v and when I touch the positive lead to the center tab and the negative to the ring tab, nothing happens.
There are no jumpers for the power supply on my arduino, it's replaced with a small chip. Also, when I exclude the capacitor, the arduino works.Thanks in advance
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M$4 Answers
A capacitor will help you and you would need to place it across the battery terminals. It needs to be 16v minimum but its capacity needs to be much higher - say 4500 uf or higher. Probably 15,000 would be better. Small values will only hold a small amount of energy. You might find a large cap like this as surplus in an old PC power supply. (The voltage rating does not matter as long as its greater than 12V)
However a simpler solution may be to increase the current capability of the battery by putting two 9v batteries in parallel as the voltage source. Or by using a bigger battery pack of D size cells - Probably 5 cells will do as 7.5 volts is over the headroom limit for the voltage regulator. You don't really need 9v but people use them because its the easiest single battery you can buy.
(If using 2 9v batteries in parallel - its important that the two batteries are both fresh and that you change them at the same time. Else one will be reverse charging the other - which is bad).
I recommend a D cell battery pack as a solution unless you happen to have a 15,000uF cap lying around (can be expensive new).
Its also possible that the voltage regulator is being overtaxed. In many cases the voltage going to the PC board is decoupled from the voltage going to the heavy current drawing part of the circuit. This is done a lot for servo control because they are driving motors and motors also generate noise as well as drawing a lot of current. This ripples on the positive voltage rail and can reset the CPU.
So in this case a separate supply is used to drive the current drawing circuit and they are both grounded together to keep the voltages correct relative to each other.
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M$1. Capacitors smooth out voltage ripple, not current ripple. If you want to minimise current ripple then you should use an inductor, but be careful about how you use it! Back emf may damage your board.
2. If i were to do such a project, I would suggest connecting the arduino to one power supply, with the output of the arduino to the input of a push-pull amplifier. The push pull amplifier is then connected to its own supply which is higher rated.
There are two good things about this, firstly you can vary the supply to the lamps. Second, if your supply drops too low then the program you are running on the board does not get interrupted by loss of power. Considering that all you need is two transistors to make this work, in my opinion, this is well worth doing.
There is a picture here of how to wire up this amplifier:
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M$While .1uF and 10uF capacitors are the commonly used values for power smoothing and local battery, from what you have described I am hesitant to believe they will solve your problem. Loose connections are the common cause for such symptoms. If you were able to provide pictures of your set up, it would greatly increase the chance of someone on this site be able to assist.
Far too much Circuit Network Analysis and Embedded work.
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M$
Right, I realized my post didn't make as much sense as I had hoped after posting.
Unfortunately, I have yet to find out how to edit.
I'm using my arduino to work with lights and LEDs, but during some moments when it's switching a handful of lights off and turning others on, it will just randomly restart.
A friend suggested placing a capacitor in the circuit between the 9v battery and the board, but so far none that I have tried have worked.
I soldered all of the connections, they seem fairly secure, I also have some pictures, but first have to upload them to another site for HAD-Ans to embed from...
The arduino is not connected to USB, except to get a new sketch.
Thank you for the input.
When I claim that none of them have worked, I'm not referring to the restarting problem, the arduino (pwr led) never turns on in the first place when the capacitor is in the loop.
Is your capacitor connected across the 9v battery terminals or from one end of the battery, to the arduino? It should connect from the positive terminal of the 9 volt battery, to the negative terminal of the 9v. The 9v battery should connect like normal to the arduino. LED's draw minimal current when compared to standard incandescent bulbs (such as the ones in old flashlights), have you tested your set up using a wall adapter? Does your arduino have the same problem if the lights are not connected? Are you driving your lights straight from the output pins or through an LED driver or transistor? Arduino's uC, ATMELS ATMEGA328 can only source a couple LEDs at most per pin, and if all pins are running, you may be drawing more power than your arduino can source, causing it to reset.
Based on your description of the problem it sounds to me like your issue is not with needing to smooth the power (this is generally only a concern with AC power) but instead simply too high of a current draw on the arduino.
If the current draw is too high the arduino will brown out and end up resetting, it seems to me like this is more likely the issue.
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M$
Thanks for the suggestions, this pretty much wraps up what I am looking for.