9V battery power supply - add dc adapter backup

BradtheRad said:

Probably you can do that. Then each relay gets 4.5V. A relay is made to pull in at a lower voltage than it is rated for.

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It may be ironic but a 5V relay takes more juice than your pedals combined. Therefore your 9V supply needs to be designed to supply sufficient power to the relay coils.

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Thanks, The power supply provides 9v 400ma regulated output. I think it will be enough.

BradtheRad said:

Probably you can do that. Then each relay gets 4.5V. A relay is made to pull in at a lower voltage than it is rated for.

- - - Updated - - -

It may be ironic but a 5V relay takes more juice than your pedals combined. Therefore your 9V supply needs to be designed to supply sufficient power to the relay coils.

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Done deal, here is a box. Everything works. Thanks for your knowelage and help.

Gee, you work quickly. Admirably neat construction.

As I think about it, there is sense to having a battery for each pedal. It ensures you can still use the other 3 pedals if one of the batteries goes bad during a performance.

pedalpower said:

Hello,
I need help with this build.
I would like to build battery power supply for my guitar pedal board. Here is a requirement.
four 9v battery, isolated one for one effect pedal. When pedals are not in use, all battery must be disconnected fron the pedals, as soon as pedal board powers on battery should kick in and provide the power to those pedals. When the power of the battery drops to some point, power supply has to provide back up, untill the battery will be replaced with new one. Each output dedicated to certan pedal. Here are the pedal current: first 11.73ma second: 1.78ma third:8.4ma fourth: 4.5 ma I prefer to use comperators and need some help with schematiss.
I'll provide more info if needed.
Regards and thanks for your help.

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pedalpower said:

Hi Klaus, Thanks for reply. Unfortunatelly a pedal builder ( Pete Cornish ) warned me to use 4 separate 9v batteries insead of one. Mason Marangella made those battery power supplies using comparators ( looks very simple, one in, four outs and I think two comparators). Should be some resistors there but I can't see them on a picture. Top of comparators covered by black foam. No PCB board. Any idea how to make it work.
Thanks, Regards,
Iouri

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Hello all!

So here's the tricky thing with the unit that I build for Michael Landau, Josh Smith, and others that you're referencing - when you're dealing with high impedance carbon batteries (which is the purpose of the unit because of the sound that the carbon batteries impart compared to DC or alkaline one), you have simultaneous current limiting along with the constant voltage drop, and to set a threshold as to when the DC "failsafe" from the main power supply would take over is tricky. The challenge in the field is that every carbon battery is a little different in the rate that it looses voltage and restricts current along with the devices that each battery is paired with and it is difficult to predict when to have the DC supply take over for the battery with any level of consistently. Some devices could function and sound good at as low at 4VDC, however others might drop out after 8VDC. Also factor in any temporary voltage or current drops that happen when the input is hit harder on these devices from both pick attack or slamming the input with more gain. It starts to add in a very complex circuit of having to set individual thresholds for each battery that are variable based on battery brand and device, which for most consumers, would be too complicated to adjust.