5v to run a 12v electronic relay?

[Sunny55]

Just wonder if i can use 5v to run a12v relay? Previously was using 13v and heard clicking sounds n relay does not work.

- - - Updated - - -

Circuit setup- converted 5v from 12v using 7805 reglulator and 5v into relay input points.

 

[tpetar]

Try something like this :

Just wonder if i can use 5v to run a12v relay? Previously was using 13v and heard clicking sounds n relay does not work.

Circuit setup- converted 5v from 12v using 7805 reglulator and 5v into relay input points.

Why to lower from 12V to 5V and then to make circus to run 12V relay ?

Also you can use relay with coil on 5V (relay is designed to work on 5V, there is 3V relay), or you can use both 12V and 5V in device, where 12V can be used just to run 12V relay.



See this relay on 5V and 3V, just as examples :

**broken link removed**

 

[Sunny55]

I have a problem with 12v relay when i use supply of 13v. Heard weird clicking sound frm relay n the switching does not work. So was thinking what will happen if 5v is used to run
12v relay ? But my load is a 12v

 

[tpetar]

12V relay should work on 13V without problem. But maybe you have bad quality product or you have more then 13V, check low cost unimer twice.

Maybe 12V relay is bad or have damaged contacts.

First test your relay on exact 12V, use ohmmeter to check contacts.

You can use one or two standard diodes in serie to lower voltage by 0,7V each.

 

[Sunny55]

I have tested the relay and the relay was able to shift as i heard the clicking.sound. the coil resistance was also non zero measured using a multimeter.

 

[tpetar]

I have tested the relay and the relay was able to shift as i heard the clicking.sound. the coil resistance was also non zero measured using a multimeter.

How to test relay. Clicking or not clicking is relative.

1. Take multimeter and switch to DC voltmeter range 20V.
2. Measure 12V voltage source. Should be 12V. Disconnect multimeter from circuit.
3. Switch multimeter to Ohmmeter position in lowest range of 20-200Ω.
4. Check connections on relay contacts, NO (Normaly Open) and NC (Normaly Conected)
5. Put + and - to relay coil.
6. Check status of relay contacts again with Ohmmeter for NC and NO.

If all is ok, repeat this test with 13V on relay coil instead of 12V.

On 13V maybe relay contacts will give stronger click.

 

[123jack]

When you say clicking do you mean contact bounce? Is it an old relay?
Also check the diode

 

[Sunny55]

123jack- which diode to check? Its a new relay
tpetar- yes i have checked the relay. Working . Could it be wire size? When i tested on breadboard with a 12v car battery circuit works fine but soldered onto a stripboard does not work sometimes . Maybe its da wire size n resistance or maybe current handling capacity?

 

[D.A.(Tony)Stewart]

When looking for power switches , remember this category...
Product Index > Integrated Circuits (ICs) > PMIC - Power Distribution Switches

Here is one of hundreds of examples.. Read the specs fully and buy a bunch. They are cheap.. <1$ but far superior to any single stage transistor and did i say cheap?

Si3861BDV
Number of Outputs 1
Rds (On) 75 mOhm
Internal Switch(s) Yes
Current Limit 2.3A
Voltage - Input 4.5 V ~ 20 V
Operating Temperature -55°C ~ 150°C
Mounting Type Surface Mount
Package / Case 6-TSOP (0.065", 1.65mm Width)

This means you can drive them from low voltage logic levels to drive 2amps easily.

better than using a relay and much more sensitive.

 

[123jack]

Sunny - Back-emf diode - A couple of links picked at random that may help:
**broken link removed**
http://www.electro-tech-online.com/...t/20794-diode-across-relay-1n4148-1n4001.html
A cap placed across the back-emf diode can also help reduce bounce

 

[ark5230]

Is there any chance that under test condition, due to controlling program etc the relay tripping is fast enough to cause this type of sound, if the relay is tripped at a rate faster than its mechanical natural frequency such situation is encountered.

 

[tpetar]

There is no mistery and nothing is magical here.

Just check relay functionality is ok or not on declared voltage.

Check voltage at relay point, and driving signal.

Check relay contacts operation.

Check connections in circuit and flyback diode.

Job and solution in 5 minutes.

 

[D.A.(Tony)Stewart]

Sunny55
You cannot activate a 12Vdc relay with 5V.

To have reliable operation they must have 66% the rated coil voltage (9V) to activate and will hold down to 10% Vcoil rated = 1.2V

A clamp diode is recommended just to protect a transistor driver from overvoltage.
The chatter sound @ 13V proves nothing. Try a load and test for contact bounce > 100mS
Verify voltage when active at coil.

Most relay coils can handle 2x rated voltage at room temp. but induce self heating.


One solution is reduce the coil current, if that is important is reduce voltage from, 13V to 9V with a 4V diode or resistor drop and do not use the 5V reg.
This has nothing to do with contact bounce, in fact more coil voltage ought to reduce contact bounce time.

Your echo sound like chatter may be your setup problem.


A better solution is use the solid state high side driver I recommended.

 

[Sunny55]

Hi, the diode should always be placed as close as possible to the relay? Can it be placed slightly further? How would it affect the performance?

 

[tpetar]

Hi, the diode should always be placed as close as possible to the relay? Can it be placed slightly further? How would it affect the performance?

Put diode close to relay coil in correct orientation.

 

[Sunny55]

Put diode close to relay coil in correct orientation.

I see that. I placed the diode in another circuit separated from the relay circuit. Maybe thats why its not working well? Its like in some pcb design where the datasheet tells you to place the components as close as possible to the ic or something.

Could you explain whats the difference in the placement position of the diode on the performance please?

 

[tpetar]

I can not even imagine what awaiting us when you start programming uC.


This is not linked with performance of relay, its protection from voltage spikes. Read material about coils when power is off, and general switching tech.

I already post material for the same question which you ask in other thread.

 

[Sunny55]

I can not even imagine what awaiting us when you start programming uC.


This is not linked with performance of relay, its protection from voltage spikes. Read material about coils when power is off, and general switching tech.

I already post material for the same question which you ask in other thread.

Ok, i get the idea. By the way, does using two types of jumper wires size in the circuit would affect circuit's stability and operation? I am just not sure but i think it would not affect the operation.

 

[tpetar]

All depends what these cables connect.

Cables should be maded from good quality copper, I supose you dont have silver wires. Also quality on cable ends is needed. Do not use very thin cables to avoid higher resistance.

 

[godfreyl]

Maybe thats why its not working well?

No. It's not working well because there's something wrong with your driving circuit. According to your measurement in your other thread, you only get 5.5V across the relay coil.