12 volts to 7.5 volts

[Preher TV]

I have the piano. It takes between 40 - 100mA. It just has five AA cells. You just need a 1 watt zener to drop the voltage from the plug pack.

Is this the keyboard, Because according to the specifications it does not draw 40-100mA it consumes 1.6 Watts at 7.5V which is around 213mA.

https://www.casio-europe.com/euro/downloads/emi/SA-45_en.pdf

 

[sammy004]

Is this the keyboard, Because according to the specifications it does not draw 40-100mA it consumes 1.6 Watts at 7.5V which is around 213mA.

https://www.casio-europe.com/euro/downloads/emi/SA-45_en.pdf

So all I need is a 1 watt zener diode in line and I'm set?

 

[colin55]

SUM-3, R6P, "AA" Size or Equiv. Batteries

SUM-3, R6P, "AA" Size or Equiv. Batteries

Look at the batteries. How long do you think an "AA" cell is going to last at a current-drain of 230mA???????
It says 6 hours with ordinary "dry cells" and since thay have a capacity of about 600mAhr at this current drain, the average current will be about 100mA.

 

[audioguru]

SUM-3, R6P, "AA" Size or Equiv. Batteries
Look at the batteries. How long do you think an "AA" cell is going to last at a current-drain of 230mA???????
It says 6 hours with ordinary "dry cells" and since that have a capacity of about 600mAhr at this current drain, the average current will be about 100mA.

It says with manganese (super heavy duty) batteries with a low volume setting. Does anybody still use super heavy garbage batteries anymore?
Alkaline cells will last a lot longer even at a high volume setting.
Rechargeable Ni-MH AA cells will last longer than alkaline cells ands can be recharged over and over.

 

[sammy004]

OK so can we get back to me question please?

 

[Mr RB]

Since the variables are STILL unknown (ie you don't know how much current it draws and you don't know what it's max safe voltage is) and we don't seem to be getting any closer to knowing, why not just get a 7808 (+8v) 3pin regulator. That will definitely fix it without any messing about and without needing exact specs.

And if you REALLY prefer 7.5v you can just put a diode on the output to drop 0.6v.

 

[sammy004]

Since the variables are STILL unknown (ie you don't know how much current it draws and you don't know what it's max safe voltage is) and we don't seem to be getting any closer to knowing, why not just get a 7808 (+8v) 3pin regulator. That will definitely fix it without any messing about and without needing exact specs.

And if you REALLY prefer 7.5v you can just put a diode on the output to drop 0.6v.

How would I put that on.

 

[Mr RB]

First you read the datasheet;
Fairchild Semiconductor 7805 Series Datasheets. 7808, 7806, 7805, 7812 Datasheet.

then you connect wires to its 3 legs.

 

[sammy004]

First you read the datasheet;
Fairchild Semiconductor 7805 Series Datasheets. 7808, 7806, 7805, 7812 Datasheet.

then you connect wires to its 3 legs.

I can't read that data sheet because I don't wanna subscribe.

 

[blueroomelectronics]

Try Google LM7805, but since you want 7.5V you might want an LM317
**broken link removed**

 

[sammy004]

I am very confused and I'm not that great with electronics just learning. I was hoping for something I can just add between the lines to decrease the voltage.

Maybe i might just easier to just but a 7.5 volt plug for about 20 bucks, but even 20 bucks seams alot when your not working.
Oh well

 

[blueroomelectronics]

The LM317 is easy to use and common.
LM317 Voltage Calculator - Electric Circuit

Maybe i might just easier to just but a 7.5 volt plug for about 20 bucks

You'll probably find that is by far your best course of action.

 

[audioguru]

I can't read that data sheet because I don't wanna subscribe.

The manufacturers have free datasheets online.
I get free datasheets from www.datasheetarchive.com then I can select from many manufacturers of a device.

EDIT: I mis-spelled the address of datasheetarchive dot com. It is corrected.

 

[sammy004]

The LM317 is easy to use and common.
LM317 Voltage Calculator - Electric Circuit



You'll probably find that is by far your best course of action.

I don't wanna sound so stupid but how do I add this to the 2 wires on the wall plug?

 

[audioguru]

I don't wanna sound so stupid but how do I add this to the 2 wires on the wall plug?

Its free datasheet shows how to do it. It needs an input capacitor, an output capacitor and two resistors.