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How can i convert 5v easily to 12v with some available parts…

How can i convert 5v...
How can i convert 5v easily to 12v with some available parts its for a small project for automotive use , parts store not open today , i need to convert 5v to power a 12v relay , i have a lot of old stuff i can scavange parts from , dvd players , usb , etc
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Answered in 2 hours by:
10/15/2017
Louie
Louie, Technician
Category: Consumer Electronics
Satisfied Customers: 13,430
Experience: 25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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Hi and welcome to JustAnswer, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially, re-confirm and post back that this is a"...project for automotive use..." hence 12V is available somewhere.
And to "...convert 5v to power a 12v relay...", the relay coil specs would be needed particularly how much current it draws to latch.

Have you considered a switching transistor enabled by 5V? ...but the relay would still be powered by 12V?

This is an independent site and members of this online community provide information, repair tips, technical assistance as a form of paid Q & A service.

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Customer reply replied 9 months ago
Hello Louie , thanks for assisting me , as i mentioned before i will need to trigger a 12V Relay comming from a 5V sensor output
Customer reply replied 9 months ago
It is a 5V output from a Ac Pressure sensor witch doesnt draw so much current

Your first approach appears to be "...convert 5v easily to 12v..." since:

  • 12V Relay; and
  • trigger...from a 5V sensor output.

And the prescribed solution is to build a DC-to-DC converter; i.e. 5V + switching regulator = 12V

However, there is an easier approach; i.e.:

  • 5V output from a Ac Pressure sensor;
  • triggers a switching transistor;
  • that turns on the 12V powered relay.
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Customer reply replied 9 months ago
But as you mentioned will the transistor help me based on my drawing , will it replace the 5Volt Relay in a kind of a way with a minimum current to trigger the 12 Volt Relay

Yes.

Consider/try:

  • diode cathode/pin 86 to a +12V supply;
  • diode anode/pin 85 to the collector of an NPN switching transistor such as a DTC143ES;
  • emitter of this switching transistor to ground;
  • base of this switching transistor to the pressure switch output.

A moment while I prep a schematic.

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Customer reply replied 9 months ago
Considering that i dont have the 5 volt relay , and using the transistor directly conected to the 5 volt to power the 12 volt relay

A 5V relay is not needed.

Perhaps it would be better to look at it this way:

  • 5V output of pressure switch needed only to turn on (not power) the switching transistor;
  • transistor's collector and emitter pins to serve as electronic switch;
  • transistor's collector and emitter pins switches relay pin 85 to ground;
  • relay energized;
  • relay contact supplies +12V to load/compressor.

Please click HERE.

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Customer reply replied 9 months ago
Ok ... Louie just some questions an bear a little patience with me as im no electrical expert... So basically what you send me or explained is the 5Volt from the pressure switch goes through the Transistor? To activate the relay?What does a transisctor literally do?
Will it provide a minimum pulse for the relay?
Any drawbacks usimg transisctors heating?
What type of transisctor am i looking for?
In what type of devices can i scavange for a transisctor?

I understand.

On:

  • 5Volt from the pressure switch goes through the Transistor? - negative; the 5V just turns on the switching transistor and is not passed/feed through;
  • What does a transisctor literally do? - Think of it as an electronic (relay) switch where the 5V is only needed to turn it on;
  • Will it provide a minimum pulse for the relay? - yes as the transistor's collector/emitter acts just like a switch. It does not matter whether you have 5 or 12 volts as it only works on or off;
  • Any drawbacks usimg transisctors heating? - none;
  • What type of transisctor am i looking for? - as posted above "...an NPN switching transistor such as a DTC143ES...";
  • In what type of devices can i scavange for a transisctor? - most electronic devices / circuit boards would have an NPN (switching) transistor.
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Please click HERE.

As shown:

  • the leftmost leg (1) would be the emitter that must be connected to the system ground;
  • middle leg would be the collector (2) and referring to my earlier diagram would go to pin 85 of the 12V relay;
  • while the right leg (3) would be the base and to be connected to "5Volt from the pressure switch".

See the video tutorial HERE for insight to determine/verify base, collector and emitter.

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Customer reply replied 9 months ago
Ok thank you very much , i will try it out , and get in contact with you again to let you know how it worked out

Yes please; an update when able.

A friendly reminder; there are several versions of the leg arrangements of NPN transistors depending on the suffix of the transistor's Part Number.

Also you may want to carefully use alligator clips with wires when experimenting connections. Please click HERE.

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Customer reply replied 9 months ago
Hello Louie i happened to find a NTE2367 they said its the equivelent of the DTC143ES , is this allright?

Yes, an NTE2367 would work equally just like the DTC143ES.

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Customer reply replied 9 months ago
Hello Louie i am a little off the tracks or confused
Customer reply replied 9 months ago
With the transistor do i have to make any changes in my drawing , first time experimenting with a transistor ,,

Please click HERE.

And if you haven’t done so, please provide a positive rating (3 to 5 stars) at the top of your page.

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Customer reply replied 9 months ago
I dont plan in using the Diode anymore in the relay , so will it still be necesary to hook 86 and 30 together ? , whats your opinion ? For me skipping the diode?

The circuit would still work even without the diode.

However, the diode protects the relay coil and in this instance, more importantly also the transistor.

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Customer reply replied 9 months ago
Time to test evryhting is hooked , ...

Ideally, test / monitor with three (3) volt/multi-meters:

  • base of transistor;
  • collector of transistor; and
  • 87 of relay.

Or test each point one-at a-time.

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Customer reply replied 9 months ago
In the last diagram you send i saw that you hooked 86 to 30. Why is that

86 is the power feed to the relay coil.

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Customer reply replied 9 months ago
im still missing something i cannot get 12v to the compressor , but i can hear the relay Buzz , any idea if i misonnected the pins of the transistor wrong?

Please post back with clear pictures of the "...pins of the transistor..." Click HERE.

These pictures would then serve as common references.

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Customer reply replied 9 months ago
ok Louie sorry to take to much of your time , i will make a drawing of what i have done , from scratch

Can you post pictures of the actual transistor, connections and relay?

These would allow me to see what you are seeing.

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If 86 is connected to the collector of the transistor, then:

  • 85 should go to '12V battery' or even 30;
  • emitter of transistor should go to ground; and
  • base of transistor should go to 'pressure switch'.
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These / above would be the correct connections to the transistor.

To test, momentarily short the red and black. The relay should click/engage.

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Customer reply replied 9 months ago
The relay just buzzes but no power to the other side

Sorry. but please complete the description:

  • relay just buzzes - when ?????;
  • no power to the other side - of what / which pin(s)?
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Customer reply replied 9 months ago
At 87 there is no power
Customer reply replied 9 months ago
When ac switch is on relay buzzes , then at 87 there is no power coming out to the compressor

I understand, "...ac switch is on relay buzzes , then at 87 there is no power coming out to the compressor..."

What are the voltages at:

  • pin 30;
  • pin 86;
  • pin 85;
  • collector of transistor; and
  • at the base?

Did you try (momentarily) shorting the black and red aliigator clips?

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Customer reply replied 9 months ago
Pin 30=12volt
Pin86= 11.56
Pin85= is hooked to pin 30 so the same voltage
Collector= voktage variation
Base= 3 volts

Did you try (momentarily) shorting the black and red aliigator clips?

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Customer reply replied 9 months ago
No havent tried that

Please try and determine if relay would engage = 12V to compressor.

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Customer reply replied 9 months ago
You mean take the aligator that feeds the 86 , or the ground from the transistor to the 86?

Yes; please short together the red and black alligator clips.

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Customer reply replied 9 months ago
sir , when i short them the relay actuates normally , whit no power on the ignition

Based on this, then the "...Base= 3 volts..." is not enough to trigger the transistor; was expecting 5V.

This is very significant as with only 3V available from the 'pressure switch', then even a 5V relay may likely not work too.

Two potential workarounds:

  • raise the 3V to 5V (least likely doable); or
  • make the transistor more sensitive (more likely - replace).
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Customer reply replied 9 months ago
What type of transistor am i looking for ??

A Darlington pair; i.e. two (2) transistors in 1 package such as a TIP122 or a 2N6387.

Louie
Louie, Technician
Category: Consumer Electronics
Satisfied Customers: 13,430
Experience: 25+ yrs. experience in the field and 5+ yrs. online, down to component level.
Verified
Louie and 87 other Consumer Electronics Specialists are ready to help you
Ask your own question now
Customer reply replied 8 months ago
Thank you very much Louie , looking forward to work with you again
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