Connecting 5V to a relay with coil voltage of 4.5VDC

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
Dear Team,

I want to use this relay. in one of my applications. The coil voltage of this relay is 4.5V .I have a 5V supply available.

Is there any problem in connecting 5V to a relay with a coil voltage of 4.5V.

The relay will be driven from Arduino. My circuit will look like as shown below.

1630170212411.png

Regards
HARI
 

MaxHeadRoom

Joined Jul 18, 2013
23,924
There normally is not a problem, relays are not usually very precise devices, Automotive is an example where the relay is 12vdc rated, and the operating voltage is 14.5v
The only version that do not like anything lower than the rated is AC types.
4.5v is rather an odd value, what is the No. of the relay?
 

Audioguru again

Joined Oct 21, 2019
3,849
The datasheet of the relay says its maximum coil voltage is 150% of the 4.5V which is 6.75V. No problem with the 5V supply and the transistor saturating to 4.85V.
 

LowQCab

Joined Nov 6, 2012
1,341
The Question is ........
Why use a Relay at all ?
A Single MOSFET will do the job.
If the Load is AC, then 2 FETs and an Opto-Isolator will handle it.
No Contacts to wear-out, no arcing, and less than ~20ma. Load from the Opto.
.
.
.
 

nsaspook

Joined Aug 27, 2009
8,905
The Question is ........
Why use a Relay at all ?
A Single MOSFET will do the job.
If the Load is AC, then 2 FETs and an Opto-Isolator will handle it.
No Contacts to wear-out, no arcing, and less than ~20ma. Load from the Opto.
.
.
.
For my application I'm switching RS232 level signals (in a high EMI enviroment) from a use port 1-monitor port 1 condition to a use port 1&2 condition. A submini Omron DPDT relay provides the needed isolation and switching in small very reliable package.
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g6k.pdf
 

LowQCab

Joined Nov 6, 2012
1,341
In that case it may well make sense to use a Relay,
but we don't know what the Thread-Starter is trying to Switch,
could be anything at this point.
.
.
.
 

nsaspook

Joined Aug 27, 2009
8,905
In that case it may well make sense to use a Relay,
but we don't know what the Thread-Starter is trying to Switch,
could be anything at this point.
.
.
.
Don't know what the OP plans to switch but using this series of relay for switching low level signals is very reliable. I've used this type of PCB relay for decades without failures other than current overloads frying the contacts.
Service life Mechanical 5,000,000 operations min. (at 36,000 operations/hour)
Electrical 100,000 operations min. (with a rated load at 1,800 operations/hour)
 

MrSalts

Joined Apr 2, 2020
728
Dear Team,

I want to use this relay. in one of my applications. The coil voltage of this relay is 4.5V .I have a 5V supply available.

Is there any problem in connecting 5V to a relay with a coil voltage of 4.5V.

The relay will be driven from Arduino. My circuit will look like as shown below.

View attachment 246771

Regards
HARI
when you write your code, make sure to set pin D12 as an input with an internal pull-up resistor (DO use a simple pinMode assignment...
pinMode(12, INPUT);

instead, use
pinMode(12, INPUT_PULLUP);

or add your own pull-up resistor for the switch.
 

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
There normally is not a problem, relays are not usually very precise devices, Automotive is an example where the relay is 12vdc rated, and the operating voltage is 14.5v
The only version that do not like anything lower than the rated is AC types.
4.5v is rather an odd value, what is the No. of the relay?
Hi Max,

P/N is G6L-1P-DC4.5

Regards
Hari
 

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
when you write your code, make sure to set pin D12 as an input with an internal pull-up resistor (DO use a simple pinMode assignment...
pinMode(12, INPUT);

instead, use
pinMode(12, INPUT_PULLUP);

or add your own pull-up resistor for the switch.
Hi MrSalts,

Thank you .I will take of that.
May I know why pull up resistor.I will be using the circuit as shown in the question.
I will put an additional resistor from base to ground also

Regards
HARI
 

Alec_t

Joined Sep 17, 2013
12,317
I doubt you'd be able to get closer than a ball-park figure for the kick-back voltage, because of unknowns such as the driving source properties and the rate of movement of the armature. Inductance will depend on how far the relay is pulled in. The usual practice is just to put a reverse-biased diode across the relay coil.
 
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