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I have set up a circuit similar to the one here. I was wondering instead of the 10 uf 50V capacitor, would A 100 uf 16 V or a 47 uf 6.3V capacitor work? I am asking because I don't know how much kickback into the hbridge there is. I know there can be enough to damage it, but how much is that? Also, how would I determine the amount of current used by a 4v motor?

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The 10 uf 50V capacitor you are talking about looks like its connected to the Power rails, and it is used to smooth out the power lines. Depending on your power supply and voltage you are using you can switch out the cap for another value, I would suggest at least double the voltage and a similar capacity. Check out this question for a better explanation. Decoupling capacitors: what size and how many?

the kickback that you are talking about is usually quite high and is taken care of by the motor driver, not something you need to worry about in this example,but double check the datasheet to be sure. when creating your own motor driver you will need to consider these conditions.

as for your 4V motor, best way to measure is hook it up to a 4V source with an multimeter in series and turn it to measure milli amps and run it for a few seconds and get the running current, next if possible stall the motor for no more then 2 secs and read the current. That will tell you your running current and stall current.

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  • \$\begingroup\$ Ok, thanks. One thing I dont understand is you say you would dou le the specs of the capacitor but you also say the motor driver is what would handle it. \$\endgroup\$ – a sandwhich Mar 29 '11 at 12:04
  • \$\begingroup\$ the link you posted shows the capacitor in the upper left corner, I didnt say double the specs, You should use at least double your Source voltage ( as in how much voltage you are putting into the motor driver) for the voltage rating of the cap. Example- Lets say source is 5V powering every thing, then you would want at least a cap rated at 10v or above. the cap is for keeping all the power stable preventing small voltage drops when the motor is running, IE smoothing the power rails. \$\endgroup\$ – jsolarski Mar 29 '11 at 13:25
  • \$\begingroup\$ Ohhh. I misread, sorry. \$\endgroup\$ – a sandwhich Mar 29 '11 at 20:55

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