V G gmail.com> writes: >=20 > On Fri, Jun 10, 2011 at 2:01 AM, IVP clear.net.nz>=20 > wrote: >=20 > > I've found with IR transmitters that a 470uF / 6V low-leakage > > makes a big difference as the batteries run out. As Sergey says, > > Vdd will droop and spike without a reservoir cap. You should > > be able to work out what capacity is need to smooth Vdd. For > > an IR transmitter the demand is fairly-well spaced bursts, giving > > the cap time to recover somewhat. You might find that your > > circuit draws too much current to be supplied like that from the > > cap, but it would still be helpful for bulk smoothing and preventing > > glitches > > > > > What type of capacitor? Tantalum? Or another kind? It almost does not matter what type. Preferably low ESR. Calculate min capacity using current * pulse time and desired volt drop. If it's a=20 one-off project, even a supercap can be used, they are relatively cheap=20 these days. Supercap is probably an overkill, 470uF as IVP suggests is a=20 good starting point. =20 Sergey http://beaglerobotics.com --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .