Need a relay recommendation

I don't think you have defined the parameters completely. What happens after the 30ms? What de-energizes the 12V circuit?

Some reed relays are notoriously sticky when driving a capacitive load. Your average current may be within the speck but if you are charging a big honking capacitor the contacts may stick and it may not open again until you give it a whack.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place

Wrong model. This needs 12 V to operate but won't switch more than 5 V. You need the other way around.

"Rated coil voltage: 12 VDC (at 20°C) Operating voltage: 8.4 VDC (at 20°C)

Try Catalog #: 275-232

ou

My mistake. I just copied the first link I came to. I am actually using the model you suggested.

The 30ms pulse is sent to a PLC input and it causes the PLC's program to start running.

During the 30ms the relay is closed, 12v is applied to the input of a PLC. When the 30ms is up, the 12v is no longer applied to the input.

My mistake. I just copied the first link I came to. I am actually using the model you suggested.

The 30ms pulse is sent to a PLC input and it causes the PLC's program to start running.

Is the relay not firing? Are the contacts welding?

Since the on time is fairly small I would suggest using an N-channel FET instead of a relay. The 5 volt output would be well in the trigger voltage spec for the gate.

Your relay is not closed for 30 mS if it is energized by a 30 mS pulse. There is some transfer time, and some bounce. If the 30 mS is critical for the PLC, a mechanical relay is not the right way to go. Here's a general circuit:

Try the circuit. Choose R as needed to limit the current to the appropriate value for your PLC circuit.

Ed

Good question. I have not taken one apart to see if they are welded. They just stopped working. I'll take one apart an see.

Would you suggest a part number I may be able to cross-reference?

But, connect the base of the NPN to the output of the timer through a resistor (33K would be good) and not directly to the +5 supply (which would destroy it)

Bye. Jasen

Just whack it with a screwdriver handle. Often it will unstick.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place

if he's using a AB Micrologic 1000 Series, they're are a pile of bad one's out there. We've replaced 3 in the last 6 months for bad memory chips. things like Corrupted programs, or CPU not initiating and so on.

I'm using a Crouzet Mellium 3 PLC. No problems with it.

The part I personally use would be an International Rectifier FET

part number IRFD120

It's a robust little FET and can be used in many applications and it's specs are high enough I doubt you would burn it out except in extreme situations. The company I work for uses it in many circuits and I have used it on many personal projects at home.

I've attached the data sheet to this message.

--- If you want to post binaries to USENET you need to post them to alt.binaries.schematics.electronic.

Most / all service providers filter them out of text-only newsgroups.

-- JF

Do you really need a relay (isolated contact closure) to start the thing or can you just use a transistor collector switching the PLC input to ground to do it?

If it's the latter (which is most likely, I think) then all you need to do is this:

View in Courier: +------+ +----->|START | | | | C | | TIMER OUT>---[1KR]----B 2N3904 | | E | | | | | GND>--------------------+----->|GND | +------+

I have seen gif / pdf / jpg files on this group for time to time.

Is it my ISP _does_not_ filter and your ISP _does_ filter ??

donald

Why? Just post a link to it on the manufacturer's website.