controlling voltage

Hello all,

I am building this project, http://learn.mime.co.uk/assets/docs/control-your-mearm-from-arduino/MeArm_v1.0_Manual_for_Arduino_v1.0.pdf

Everything is fine with assembly. I guess I need to have a external power supply of 5v 2a to power these five servos. However I also have some other hardware that I would like to go requiring 12V 0.3a - How does one go about changing the voltage amperage?

What I’m currently thinking… I plug in a power supply of 12 volts 2amps and reduce the voltage somehow to the servo main power line and reduce amperage for the other piece?? haha sorry guys first robot here…

thanks
fitz

You normally reduce voltage, but not current.

Devices [u]draw[/u] the current they need, and servos can draw over 1 Ampere each. So, 5V at 2A will probably be too little for the servos, in which case they will malfunction. Better to have a 5V power supply capable of supplying 5A.

Use a step down regulator to reduce 12V to 5V. It must be able to handle the entire current required.

the whole voltage amperage thing just kindof clicked for me. so everything I need before 5v I can do before I use the step down regulator. Is there another way to do this? seems like it wouldnt be very efficient if you need to had something complex like a computer. Any idea?

kidfitzz: so everything I need before 5v I can do before I use the step down regulator.

I think you mean run the 12V stuff from 12V and the 5V stuff from the step-down converter, yes.

Is there another way to do this? seems like it wouldnt be very efficient if you need to had something complex like a computer. Any idea?

Modern gadgets can have many many regulators dotted around - its normal to step down at the point of use so to avoid voltage drops in the wiring and interconnect. Designing power supply networks is always more complex than you'd expect in my experience - so many possibilities and factors. Its always a relief when a device or circuit only needs one voltage rail.

In the good old days all(*) logic was 5V, you didn't have to worry about 3.3V, 1.8V, 1.2V or anything like that, but it was much more common to have +/-12 or 15V for analog stuff (including ADCs and DACs).

(*) Nearly all. 4000 CMOS being a notable exception.

hey thanks for your reply It also gave me a lot of relevant information.

Yes I'm pretty new at this and having fewer voltages to worry about would be one less variable!

Anyway I did mean 12V good catch haha!