Adjusting voltage

Thread Starter

x11

Joined Dec 25, 2019
5
I have a servo and an actuator, both connected to a breadboard, needing 7v and 12v power respectively. I don't want to use batteries. How would I adjust the wall plug 120v to 7v and 12v respectively? There are technically adapters on amazon, but I am not sure how to connect them to my breadboard.
 

wayneh

Joined Sep 9, 2010
16,236
I'd consider an old computer power supply. They will deliver both 12V and 5V in abundance. I know you said 7V but that servo will probably work just fine with 5V.
 

dl324

Joined Mar 30, 2015
9,984
Another option is to use a laptop power brick. They provide around 18V at 4-6 amps. Have it power an adjustable voltage regulator or, in your case, two.

Depending on the current required for your circuits, linear regulators such as LM317 or 7812 may be fine.
 

djsfantasi

Joined Apr 11, 2010
6,127
I'd consider an old computer power supply. They will deliver both 12V and 5V in abundance. I know you said 7V but that servo will probably work just fine with 5V.
If not, boost the 5V to 7V. The 5V from a computer power supply likely can supply enough current for the 7V.
 

MisterBill2

Joined Jan 23, 2018
5,177
I'd consider an old computer power supply. They will deliver both 12V and 5V in abundance. I know you said 7V but that servo will probably work just fine with 5V.
I would AVOID even considering using an old computer power supply because they demand a load current of several ams be drawn from the 5 volt output to avoid shutting down. Also they are large and have a noisy fan.
 

MisterBill2

Joined Jan 23, 2018
5,177
In addition to those 19 volt laptop computer "power bricks" there are many similar looking ones that supply 12 volts at up to several amps. Using one of those along with an additional regulator to get 7 volts would work.
BUT based on your question it is not likely that you are able to build such a circuit.
So forget Amazon as a source and check the Digikey on-line catalog for power supplies. They have a vast array of products and an adequate set of product descriptions, while many Amazon suppliers will not even provide a product part number with your order.
 

BobTPH

Joined Jun 5, 2013
2,254
Do you have the specs for that servo?

7V is a very odd voltage, I suspect that is tha nax voltage it can handle and it is designed for operating at 6V.

Bob
 

MisterBill2

Joined Jan 23, 2018
5,177
Max makes a very good point. We have no information as to the amount of power needed or what kind of servo device. So for useful advice please provide more details.
 

wayneh

Joined Sep 9, 2010
16,236
... they demand a load current of several ams be drawn from the 5 volt output to avoid shutting down. Also they are large and have a noisy fan.
I'm sure there are PSUs like that out there, but I've never encountered one with those problems. In fact my favorite is a Sony from an old MacSE. No fan, so completely silent. And it supplies 5v regardless of load up to ~10A. I do use an automotive dome light on the 12v side. Otherwise the voltage creep up to ~16V.
 

MisterBill2

Joined Jan 23, 2018
5,177
Every power supply for a desktop cased computer that had a power supply for the mother board and assorted drives and accessories has needed a load on the 5 volt output so that it would not shut down. Of course that may not apply to current production units, but it certainly was the case with the dozen units that I checked. The external supplies for portable computers are a totally different case, and I was not referencing them.
 

wayneh

Joined Sep 9, 2010
16,236
Every power supply for a desktop cased computer that had a power supply for the mother board and assorted drives and accessories has needed a load on the 5 volt output so that it would not shut down.
Not every. I don’t have any that behave that way. Most of mine are from Macs, so maybe that’s the difference.
 
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