custom fx pedal questions

[sbgodofmetal]

or even individual power for that matter wire the pedals in chain but to each its own battery but as good an idea as it is the box is getting awful crowded and would be prone to over heating with 3 rc batts running simultaniously wich could potentially fry circuits if not caught and shut off in time. unless i adjust the box design to comp for that with heatsheild inbetween the boards and batts(RC batts tend to heat up under extencive use and if compartment is not ventilated or air cooled, can cause damage)

[JohnH]

I just thought Id chip in on batteries and power.

I don’t think you need worry about heat build up with the power draw of such stomp box circuits. Its different to devices running motors and lighting which need to provide much more power. Typical stomp box circuits can use anything from less than 10mA for a simple overdrive, 25mA for a chorus, to 50-60mA for a digital delay for example. You should be able to run everything you are talking about with say 100mA, probably half that for boost, drive and chorus.

That being said, something more than a single 9V battery would be advisable IMO. Battery capacity is measured as current x time, in mA.Hours. A typical 9V battery can do about 600mAH, but after supplying that much, its voltage is down to about half. Maybe 400mAH is more reasonable. So one battery will only provide a few hours. A cheaper way to provide battery power, instead of having several 9V cells in parallel, would be to use 6xAA size cells. You can get a plastic holder with a single battery clip, and i think they can have 4 to 5 times the capacity of the 9V battery, to provide the same voltage. You can put your rechargeables there too. You also have the option of Lithium cells, which have more capacity and also much more voltage stability during their life.

Cheers

John

[ashcatlt]

Is there some reason you're adverse to a wall wart? I never use batteries. Hate them, in fact, for pedal power. They're expensive and require constant maintenance (either replacement or charging), lose voltage and cause circuits (especially the digital delays on which I depend) to work funny. I converted my Big Muff to take wall wart power so I could start using it again. I don't use my Vox wahs because I haven't found a good solution to they're power needs yet.

/rant

[sumgai]

Another note about batteries.....

They can be placed in parallel, but watch out!!

A battery is not only a power source, it's also a power drain. The word we're all familiar with here is "load". That's because there is a certain amount of resistance in any battery, but standard lead-acid, lead-zinc and alkaline are the worst in this department. Accordingly, one battery can act as a load for another battery, when they are hooked in parallel.

Here's the skinny: If battery A has a lower charge than B, it drains B until they are both at the same voltage. But no two batteries have the same internal resistance, so it's a sure bet that B is no longer up to snuff, and is thinking that it needs a recharge. Wouldn't you know it but there's good old A, ready and willing to help. Lather, rinse and repeat, and pretty soon both batteries are dead, because they spent all their juice trying to keep the each other charged!

For this reason, when we need more current capability than one battery can supply, we use steering diodes to prevent battery interaction from draining each other. That results in a minor voltage drop, but at least that's a known quantity for which we can plan.

Better yet would be to resurrect newey's idea of a few years ago, and use several cordless phone batteries in series. These are usually 3.7v Li-ion types, so they hold a charge a long time, and deliver nearly full voltage before finally dropping dead (and needing a recharge). That avoids the steering diode requirement, and if my memory is correct, these things should last an easy 50 to 100 hours of total drain usage. Remember, they're designed to power small transmitters - there's a significant amount of available power in there. Some forethought in one's design would allow for an external charger to be plugged in to the box, so that the batteries wouldn't need to be removed in order to be recharged.

HTH



sumgai

[sbgodofmetal]

sumgai...thats a good idea on the external charger so no battery removal is needed
ash... i wanted batteries because i dont always have access to a plug and the only amp i own is also battery powered
@johnhh... that was very informative i'll be using a 9.6volt rc ni-cad battery pack its 8 rechargable AA's stacked

[jcgss77]

Hey sb, you might want to try this out if you have the cheddar and some grits...nice little idea from dano at beavis audio research.

www.beavisaudio.com/techpages/PedalHacker/OrderSwitcher.htm

That guy really thinks outside the box. I hope he comes back with some more of his ideas. I am sure you probably have an order established with your style, but this really helps to see what sounds good where in your chain.