How activate loads with a higher voltage than the digital circuit gives?

Thread Starter

Doppler2902

Joined Sep 15, 2020
15
Hi guys, I'm implementing a irrigation system control using logic gates that works with 5 V, for example I have a fill valve that uses a DC Motor that works with 12 V, my question is, how I can increase that 5 V to 12 V for a correct working of the DC Motor? I was thinking in a Amp Op but I don't know what's the best alternative, thanks.
 

ericgibbs

Joined Jan 29, 2010
12,215
hi D,
You need a 12V voltage source and say a transistor to switch the 12v valve ,using a 5v drive to the input of the transistor.
E
 

bertus

Joined Apr 5, 2008
21,239
Hello,

It can be done with a transistor (BJT) or mosfet:
Switching_BJT_vs_Mosfet.png
For the mosfet you must take a logic gate version.

Bertus
 

djsfantasi

Joined Apr 11, 2010
7,551
You can’t get 12V from 5V for free. An OpAmp would need a 12V supply to convert a 5V signal to 12V. There are voltage multiplier circuits (google that), but they’re not simple.

Do you have a 12V supply for the fill valves? Then, you can use a logic level mosfet to switch the 12V using a 5V signal. You can even use the 12V to supply a 5V voltage regulator for your logic.

BTW, is your 5V logic gates discrete components or are you using a microcontroller to turn the fill gates on and off?
 

Yaakov

Joined Jan 27, 2019
2,362
Hi guys, I'm implementing a irrigation system control using logic gates that works with 5 V, for example I have a fill valve that uses a DC Motor that works with 12 V, my question is, how I can increase that 5 V to 12 V for a correct working of the DC Motor? I was thinking in a Amp Op but I don't know what's the best alternative, thanks.
Is this a commercial or industrial project? A prototype? A custom system?
 

Thread Starter

Doppler2902

Joined Sep 15, 2020
15
You can’t get 12V from 5V for free. An OpAmp would need a 12V supply to convert a 5V signal to 12V. There are voltage multiplier circuits (google that), but they’re not simple.

Do you have a 12V supply for the fill valves? Then, you can use a logic level mosfet to switch the 12V using a 5V signal. You can even use the 12V to supply a 5V voltage regulator for your logic.

BTW, is your 5V logic gates discrete components or are you using a microcontroller to turn the fill gates on and off?
Hello, I'm using discrete components
 

AnalogKid

Joined Aug 1, 2013
9,042
A 12 V load device needs a 12 Vdc source capable of supplying enough current to run the it. The most simple way to do this is to have a separate 12 V power supply, or a single supply with both 5 V and 12 V outputs. If your only available DC voltage source is 5 V, a more complex solution is to use a boost converter circuit to create 12 Vdc from 5 Vdc. However, this increases the 5 V power requirement significantly. For every amp of current at 12 V you need over 1.5 A of current at 5 V.

However you come up with the correct power system, switching a 12 V load on and off with the output from a 5 V logic gate is pretty simple. Figure out your power situation and post a wiring diagram so we know what we have to work with.

ak
 

DickCappels

Joined Aug 21, 2008
7,157
The simple answer is to use a relay with a 5V coil.

If you provide more details you might get a more satisfying solution. What does the 12V load look like (volts, amps)?
 
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