# How to drive 5V DC relay from 50V DC source(Need a 50V to 5V logic level converter)?

#### Sudip Mandal 2

Joined Mar 29, 2017
27
I want to drive a 5V DC relay from a 50V DC power supply for that I am thinking to use of a linear voltage regulator which will step down the 50V to 5V. I will use TPS7A1650DGNR or NCV8141D2TR4G LDO as regulator like this way...

But Its a very bad Idea cause this is not logic level converter also The LDO will dissipate huge power in terms of heat and sluggish nature which will cause for relay chattering at the time of transition High to low and low to High . I cant use a voltage divider to drop voltage 50V to 5V cause the current will not sufficient to drive relay. I cant use 50V DC relay cause space is limited also SMT version is not limited.

Is there any procedure to 50V DC to 5V dc logic level converter?

#### Dodgydave

Joined Jun 22, 2012
8,866
Does it have to be a 5V relay, will a 24V do?

#### Sensacell

Joined Jun 19, 2012
2,567
How about a single series resistor?

Just use one power resistor, it's not efficient, but it's bone simple and dirt cheap.

#### LesJones

Joined Jan 8, 2017
2,522
Why do you have to use a relay with a 5 volt coil ? A 48 volt coil would seem to be a much better choice.
If you have a 5 volt supply at the point where the relay is you could use an opto isolator (Or just a transistor / mosfet if you did not need isolation between the 50 volt and 5 volt supplies. ) An opto isolator only requires a few milliamps to drive it. A 5 volt relay will need 10 times the current required by a 50 volt relay of the same size.

Les.

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#### ci139

Joined Jul 11, 2016
1,195
Is there any procedure to 50V DC to 5V dc logic level converter?
(((( even if there were you had to provide the +5V for the ""LOW""" side of it ))))
but there is numerous ways to produce 5V from the higher voltage
by what you describe - you need a one with the minimal startup time ← but this adds the number of components to your design

. . . the relay coil can be driven and with rectified AC or square-wave
so you need a fast start-up oscillator and voltage converter transformer https://www.electronics-tutorials.ws/transformer/auto-transformer.html https://en.wikipedia.org/wiki/Autotransformer . . .but i don't think it

has a preference over high frequency step down http://www.ti.com/product/LM5166 $3.2...3.6 (https://www.ti.com/store/ti/en/p/product/?p=LM5166EVM-C50A) + likely a cheaper alternate http://www.ti.com/product/LM5008$3.0 ? not that much

but you must verify you can draw the required power from the 50V logic-HIGH /// if not you need to get the power by other means and use some sort of level translation like http://tinyurl.com/u6l5kbh (i always think too complex) the option 2 : http://tinyurl.com/td2lxzr

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