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Electronics Forum / Basics / May 2006Millamp drama!
Hiya I recently bought two transformers for my two guitar pedals. The transformers are regulated voltage, you choose the level of voltage you want on the side. The pedals run on 9v batteries, and I think these give out 300 millamps of current. The transformer says '500 mA'. I don't know if this means it will force 500 mA into my pedal or not. The transformer also says 'use instead of batteries' so that makes me think it would be ok with the pedals, but I just want to check with some people who actually know something about electronics before I plug them in and wear down the circuits. The pedals themselves don't say anything at all about what kind of current they want. Thanks a lot for reading, advice really appreciated, as these pedals were expensive! > Hiya > [quoted text clipped - 19 lines] > Thanks a lot for reading, advice really appreciated, as these pedals > were expensive! You have to be very careful when trying to power these things externally. The best thing to do is to send me the pedals. I have several guitars and a couple of different amplifiers. I'll do a complete analysis of their power requirements. It may take me a while so you'll have to be patient. It's really in your best interest to do this. Really. Bob > Hiya > [quoted text clipped - 5 lines] > The pedals run on 9v batteries, and I think these give out 300 millamps > of current. The batteries ? They certainly won't supply that much for very long ! > The transformer says '500 mA'. I don't know if this means it will force > 500 mA into my pedal or not. No it won't. Can't in fact. It's simply the maximun rating it can supply. The same way an ac mains socket can supply 15 amps ( USA ) but the equipment plugged in just draws what it needs. > The transformer also says 'use instead of batteries' so that makes me > think it would be ok with the pedals, but I just want to check with [quoted text clipped - 6 lines] > Thanks a lot for reading, advice really appreciated, as these pedals > were expensive! They'll be fine. Graham > Hiya > [quoted text clipped - 8 lines] > The transformer says '500 mA'. I don't know if this means it will force > 500 mA into my pedal or not. Nope, it means that each one can cope with feeding a device that wants to draw up to 500 mA before getting into "You just might make this supply explode" territory.  SignatureDon Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info >Hiya > [quoted text clipped - 8 lines] >The transformer says '500 mA'. I don't know if this means it will force >500 mA into my pedal or not. It means that it is spec'd to supply its rated voltage when loaded to 500 mA. Note that many wall-warts aren't tightly regulated and may deliver, say, 12 or 15 VDC when lightly loaded on the 9 V tap. Shouldn't normally be a problem but it's wise to match the supply's load rating with the load that it will be driving. >The transformer also says 'use instead of batteries' so that makes me >think it would be ok with the pedals, but I just want to check with >some people who actually know something about electronics before I plug >them in and wear down the circuits. Shouldn't wear them down but it might heat them up. If you have access to a voltmeter, check the actual voltage delivered to the pedals in use. SignatureRich Webb Norfolk, VA >>Hiya >> [quoted text clipped - 14 lines] >normally be a problem but it's wise to match the supply's load rating >with the load that it will be driving. The key word here is 'regulated' in the original post. This means constant voltage is assured up to the rated current at least. They'll be fine for the pedals. >>The transformer also says 'use instead of batteries' so that makes me >>think it would be ok with the pedals, but I just want to check with [quoted text clipped - 3 lines] >Shouldn't wear them down but it might heat them up. If you have access >to a voltmeter, check the actual voltage delivered to the pedals in use. -- Australia isn't "down under", it's "off to one side"! stanblaz@netspace.net.au www.cobracat.com (home of the Australian Cobra Catamaran) http://groups.yahoo.com/group/cobra-cat/ > Hiya > [quoted text clipped - 5 lines] > The pedals run on 9v batteries, and I think these give out 300 millamps > of current. those batteries can give much more than 300mA. The effects pedals are unlikely to want even 300mA though. > The transformer says '500 mA'. I don't know if this means it will force > 500 mA into my pedal or not. 500mA is the "max carrying capacity" exceed it and it'll not work so good and possibly soon stop working. > The transformer also says 'use instead of batteries' so that makes me > think it would be ok with the pedals, but I just want to check with > some people who actually know something about electronics before I plug > them in and wear down the circuits. equipment for 9V batteries it typically protected against the battery being reverse connected. So the worst it can do is not work or cause a hum sound. (but regulated probably won't hum much, so it'll most likely work) > The pedals themselves don't say anything at all about what kind of > current they want. > > Thanks a lot for reading, advice really appreciated, as these pedals > were expensive! you're pretty safe there. once it's working put some glue, or reinforced tape, on the voltage switch so it doesn't get bumped into the wrong setting. Bye. Jasen >Hiya > [quoted text clipped - 19 lines] >Thanks a lot for reading, advice really appreciated, as these pedals >were expensive! It was wise to ask before just plugging it in to see it it works or blows a pedal. If the "transformer" is really regulated then go for it, it'll be fine. It will supply 9v with a load up to 500ma and a pedal is very very unlikely to need that much current. A 9v batter wouldn't last long at all if the pedal were drawing 500ma from it. Regulated just means that it will hold the output voltage fairly constant as long as you draw 500ma or less from it. Mike Everyone, thanks a lot for all the help you've given. Really appreciated. > Hiya > [quoted text clipped - 8 lines] > The transformer says '500 mA'. I don't know if this means it will force > 500 mA into my pedal or not. No I won't force current in, thats the max current the transformer can supply. Notwithstanding wrong voltages, shorts or anything else, the pedal (or any load) will take as much as it needs. > The transformer also says 'use instead of batteries' so that makes me > think it would be ok with the pedals, but I just want to check with [quoted text clipped - 6 lines] > Thanks a lot for reading, advice really appreciated, as these pedals > were expensive! If you have a pedal taking 300mA, then a 500mA will do. It is never a good idea to have a 500mA load on a 500mA supply as it cause heating. A 600mA load on a 500mA supply will give your transformer a cardiac arrest, lots of smoke and maybe a fire. Not a good idea. To be honest, you biggest problem here is polarity. Guitar pedals (like ones I use) really don't see the funny side of getting + and - the wrong way round and you need to find this out before plugging in. I actually have a voltage regulator connected to my PC supply to give me 9v for my pedal and the output drives into my soundcard. Graham. |
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