12V DC Relay Issues (Diesel Engine)

[Holden Customs]

Or just a link to the type of relay. The point here is that the different models of sensor have different output circuits; one requires the relay coil return to positive, one requires it to go to negative, one probably doesn't matter. The sensor's 100mA output current rating is sufficient to drive some relays but not all; yours may well be presenting it with a borderline overload and triggering its output protection if the coil resistance is too low.

Re wiring, no, the cable size is more or less immaterial at these low currents, any normal cable physically strong enough to use will be ample for the sensor circuit unless it's tens of metres long.

Hello. I wont be able to get the full type number of the sensor for about 3 weeks as it is on our machine at another spot in the country. As for the relay I am using it is this one attached. I think I am starting to see what you are saying. Thanks for the help.

 

[marconi]

I have tried a number of searches using the pico relay information but been unable to find out its coil resistance. Could you measure it or measure the current flowing through it at 12V? Then Lucien Nunes will have the information he needs on it.

 

[dmxtothemax]

QUOTE - is there a different relay I can use?
YES !
Use an electronic relay

3-32VDC Solid State Relay 240VAC at 3A | Jaycar Electronics

This is a PCB mounting, single in line package relay capable of switching up to 240V AC at 3 amps. Solid state relays are particularly useful when onl...

www.jaycar.com.au

 

[DPG]

The solid state relay option is a good idea.

 

[marconi]

Re #43; Good idea but I don't think the one you pointed to is suitable because it is designed for ac switching applications, the minimum mains voltage from spec is 24V and it is a zero-crossing device so will need a sinusiod main power input to trigger the conduction of the thyristors. It relies on the ac current regularly being zero to turn off when the dc control voltage is removed.

A transistor or another relay is probably a better bet. We will have to wait for Dr Nunes...

 

[DPG]

Good point Marconi.

 

[Lucien Nunes]

That is a general purpose automotive style relay, which are usually rather insensitive and require high coil current. I would be surprised if it did actually use more than the 100mA available. as it would get quite warm dissipating a nominal 1.2W, but we can't tell.

See this link for an example of an industrial product that would definitely work if the sensor model you are using has a 100mA output. This switches up to 25A using 500mW coil power. The 12V version has a resistance of 300Ω so will use 40mA at 12V or 50mA at the system's likely highest voltage of 15V. Socket bases with screw terminals are available to suit. You should add a protection diode (e.g. a 1N4007) or buy a base with one built in. There are bazillions of other options, just look for relays with coil resistance of no less than say 250 ohms.

46.61.9.012.0040 | Finder Plug In Relay, 12V dc Coil, 25A Switching Current, SPDT | RS

uk.rs-online.com

Of course, if the relay is not taking in excess of 100mA, it's not the problem, but as yet we can't tell.

 

[Holden Customs]

I have tried a number of searches using the pico relay information but been unable to find out its coil resistance. Could you measure it or measure the current flowing through it at 12V? Then Lucien Nunes will have the information he needs on it.

Thanks. I will be able to measure it once I am back with the equipment. I am away until August 12th unfortunately. But when I am, I will update it on the thread. Thanks again to everyone for the continued help.

 

[Holden Customs]

That is a general purpose automotive style relay, which are usually rather insensitive and require high coil current. I would be surprised if it did actually use more than the 100mA available. as it would get quite warm dissipating a nominal 1.2W, but we can't tell.

See this link for an example of an industrial product that would definitely work if the sensor model you are using has a 100mA output. This switches up to 25A using 500mW coil power. The 12V version has a resistance of 300Ω so will use 40mA at 12V or 50mA at the system's likely highest voltage of 15V. Socket bases with screw terminals are available to suit. You should add a protection diode (e.g. a 1N4007) or buy a base with one built in. There are bazillions of other options, just look for relays with coil resistance of no less than say 250 ohms.

46.61.9.012.0040 | Finder Plug In Relay, 12V dc Coil, 25A Switching Current, SPDT | RS

uk.rs-online.com

Of course, if the relay is not taking in excess of 100mA, it's not the problem, but as yet we can't tell.

Thanks. I will update with the measured amount when I can. If it ia what you are saying then hopefully I can get a mew relay together like you suggested.