# Circuit design to vary voltage and switch outputs

I'm new to the scene and I don't know where to start or terminology, so any advice or links are appreciated :)

What I need to build is a Magic Box™ that turns 120v AC into variable DC (0-15v) at 1 amp. The trick is that it needs to have 5 outputs, each with their own pots to vary voltage but only one output can be on at a time

So, kinda like a radio button I'd like each of the 5 outputs to have a momentary switch that, when pressed, switches the corresponding output to 0-15vdc at 1 amp and cuts power to the previous output. Like I said above, I'd need each output to have it's own voltage pot.

Finally, I'd need to have one LCD that shows how much voltage is going to whatever output is currently selected (± 0.05v). I'd prefer having 1 screen that switches with the output instead of 5 separate screens.

I'm not asking anyone to sketch this out for me! But if there are links to similar projects, I'd like to see them!

Unfortunately I'm not familiar enough with the terminology to know where to start, so if you could let me know what general parts I would need, it'd be very much appreciated!

Thanks

First way to do this that comes to mind would probably be:

(1) Find a reasonable AC to DC converter with Vout

(2) Find 5 DC-DC converters capable of stepping Vout to 0-15V based upon sensed resistor value

(3) Each of the above 5 DC-DC converters should have enable pins (most do) this will allow you to turn them on and off... along with control via resistor sense mechanism

(2) Find suitable microcontroller (MCU), with Analog to digital converter (ADC) and some variety of com protocols (SPI, I2C, UART....)

(7)connect voltage controlled resistor to sense of each DC-DC converter

(5) Hook the MCU up to each of the enable pins (one of the MCU pins to each)

(6) Purchase capacitive (or resistive) touch LCD screen with com interface compatible with MCU

(7) Program MCU/LCD combo to have touch screen buttons that let you select which DC-DC converter to enable

(8) Program MCU/LCD combo to have voltage selection slider and to display current output voltage

(9) Have MCU ADC output votlage level necessary to all voltage controlled variable resistors to produce selected voltage.

• Thank you for the advice! I'll look into all of this tomorrow :). I've heard that amperage doesn't matter and the devices will only take what they need. Is this the case? Can I disregard amperage as long as the outputs can supply at least 1a at 15v? The outputs will generally be hooking up to DC hobby motors – Kieran E Mar 5 '17 at 9:13
• Yes that is correct. If you have a regulator that can supply up to 1A (probably want up to 2A to be on the safe side... always good to double needed values), and you connect a device that wants to drain 500mA... then it will only drain 500mA. The key word is "up to" as in: up to 1A or up to 2A. – Wolfgang_Horton Mar 5 '17 at 9:17
• However it is important to note that there are some devices that will drain much more current than they can handle!! (Lithium Ion Battery for example) if you have no form of current control/limitation. So you need to consider your application. Sorry for the previously deceiving post! You need to verify that the device/circuit you are connecting will not damage itself in this way (but again... most wont) – Wolfgang_Horton Mar 5 '17 at 9:19
• Most devices have a recommended voltage to work at and then they will just drain whatever current they need at the time. You just need to make sure that you can supply the max current they ever need. – Wolfgang_Horton Mar 5 '17 at 9:21
• Thank you for all the help! I think you've set me in the right direction – Kieran E Mar 6 '17 at 2:37