Power Supply Circuit Help
Power Supply Circuit Help
(OP)
This is probably a simple question, but I'm more of a computer guy with some experience in logical circuit design (i.e., electricity is not my strong point). I need to know how to build a power supply circuit for a project I'm working on, and here is a description of it: We have a basic circuit with a microcontroller that interfaces with an LCD screen and a keypad (nothing fancy, low power draw). We also have four motors that interface with the microcontroller via relays. These motors each draw upwards of 1.8 amps or so when turned on.
Here is my problem: I need to build a power supply that can handle powering the basic circuit and the four motors. When I power all of it using the same power line (even with a supply that is more than capable of providing the current), the motors won't run. I'm assuming there is some kind of current bottleneck in my circuit somewhere. When I use completely different power supplies though (one for the circuit and one for the motors), then they work. How would I go about building a power supply with completely separate power lines then? Is it enough to have one transformer with separate voltage regulators, or would I need separate transformers too? Does any of that make sense?
Thanks for your help!
Here is my problem: I need to build a power supply that can handle powering the basic circuit and the four motors. When I power all of it using the same power line (even with a supply that is more than capable of providing the current), the motors won't run. I'm assuming there is some kind of current bottleneck in my circuit somewhere. When I use completely different power supplies though (one for the circuit and one for the motors), then they work. How would I go about building a power supply with completely separate power lines then? Is it enough to have one transformer with separate voltage regulators, or would I need separate transformers too? Does any of that make sense?
Thanks for your help!





RE: Power Supply Circuit Help
You didn't say anything about the supply voltages of the micros and motors: same? you mean the motors run at 5V (or less), drawing 2A?!
Basically, if you use a separate regulator for the micro/lcd, with good filtration AND use separate ground lines for the electronics and motors, you should be ok.
RE: Power Supply Circuit Help
You should have a supply big enough to run the motors that is unregulated. Then heavily filter some of this unregulated power and regulate it. Send this only to the micro.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Power Supply Circuit Help
RE: Power Supply Circuit Help
Then you have some decent head to run the 5V regulated output.
Normally one runs motors of that ilk with transistors not relays. Relays wear out! Also you can't do speed control or mechanical shock limiting. With transistors you can PWM the power to the motors and have them start smoothly and in a controlled manner and run them at any voltage you want. Transistor would likely cost less than relays too.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Power Supply Circuit Help
RE: Power Supply Circuit Help
Thanks!
RE: Power Supply Circuit Help
It can range from about 1.2 x the load VA to 2.4 x the load VA.
If you are just using a rectifier and caps that's about as bad as it gets.
If you are just doing a one-off figure out your maximum power needs and just get a transformer that's 2x what that comes to.
Note you can also just buy an unregulated supply that has all this figured for a maximum current rating.
Keith Cress
kcress - http://www.flaminsystems.com