Relay Usage?

[bigmil]

Hello,
I am a Mechanical Engineer and I am alittle lost here. This should be simple. We are try to hook up a automatic kill switch, so that when one piece of equipment goes down the other will shut down aswell. With the 1st machine we have a signal coming out that is .75V when it is on and 0V when it is off. The 2nd machine we have two terminals that when touched together will shut that machine off properly. I was thinking just hook up a relay to the .75V so when it goes off the relay connects the two terminals. Now I don't even know if that would work, but if it would, I am having a hard time finding a relay that would work? Is this possible? And if so where do I look for a relay? A coworker had mentioned something about a transistor, but from what I can remember, that wouldn't switch the power off?
Thankyou for the help,
Bigmil

 

[don01]

hi bigmill.
you have a signal that is 0.75v when the unit is running????
this sounds like it might be a current or instrument signal.
You should be able to fit an auxillary contact to the contactor of the "primary" unit and use this to "interlock" the next unit. There may even be a normally open contact already available on the contactor or starter. (this is usual even on VFD drives)
If the 0.75v is an instrument signal you should contact one of the instrument companies and buy an off the shelf unit.
there is a possibility that you have a transistor output from the device which will need to use the signal power of the device. (0.75v sounds like Vbe on a transistor too). If so don't connect outside power to the signal terminals.
I suspect any 1/2 decent sparky should be able to do this for you.
Don't forget if you put an interlock in the control of the second drive the second drive will not start until the first has.
now if all this doesn't help give us some data on what system you have and I'm sure someone in this group will be able to help

regards Don

 

[bigmil]

This is all of the information I have on the equipment: DC, Voltage when equipment is on is .75V, Voltage when equipment is off is 0V, Current on is 1.1MicroAmps. The input requirments for the second machine is nothing, all I have to do is connect two terminals together on the back of the machine and it goes through its shutdown. So I don't need to put any power in.
Just in case here are a few more details: Machine 1 is a oil fired burner, machine two is a computer controled electrodynamic shaker. When the burner faults out it automatically shuts off, we want our shaker to shutdown when the burner faults out. The terminals for the shaker are on the back of the computer and the terminals for the burner come out from a control box. The output signal is just an extra terminal on the bottom of the box. As far as sparkies go, we are not sure if a regular electrician could do this or if we would need someone more specialized. But I would rather do it myself. We have had bad experiences with sparkies in the past.

Thankyou,
Bigmil

 

[don01]

hi again big mill
I was just off to bed when I saw the new post. So lets try to take advantage of the real time thing while i'm up.
It sounds like you are looking at the burner management module. and the output signal is from the flame detector? Does this sound right.
1.1 Microamps will not do much good holding in a relay.
maybe you could use a meter with a contact (yeah they do make em) to provide the contact for the relay.
another thought is if this is a burner it probably has a fan. This will run from a contactor -a good place to pick up a relay supply. But that will run during purge cycles pre and post fire.
There should also be a fuel valve output this might be an in

what do you think
I'll wait a little to see if you reply if not I'lll ponder this tommorrow at work and getback to you .
PS not all us elec will zap ya but there are always one or two bad eggs

 

[don01]

its wednesday now so goodnight check in later (afternoon)
Don

 

[busbar]

Long shot:

http://www.actionio.com/support/datasheets/actionpak/ap1080-90.pdf

 

[rhatcher]

The burner management module may have a set of dry contacts that change state when the burner faults. If not, then you should check to see if a 'fault indicator' lamp is present. If so, you may be able to use the same signal to control a relay w/ normally closed contacts. This relay can be placed in the stop circuit or the interlock circuit of the shaker controller to stop it in case of a burner fault.

 

[NormGA]

This sounds like a good application for a small PLC. Go to the PLC forum791 and post the same question. You can also go to Automationdirect.com and see what they have.

http://store2.automationdirect.com/cgi-bin/ncommerce3/ExecMacro/plcdirect/homeframe.d2w/report

 

[don01]

back again
had a small rat thru some data today but not a lot of time.
Now I'm thinking rhatcher is close to the mark.
If you are only concerned with a trip or fault situation pick off the fault indicator for the burner with a relay.
If you don't want to dump material thru the shaker unless the burner is running then have a look for the fuel valve out put.
Match the voltage of the above for your relay and use a normally closed for the fault output or a normally open for the fuel valve.(relay in parrellel)
Being an oil burner it probably has a gas pilot, don't use this valve.

But Whatever you do don't stuff with the actual burner management setup. Its a quick way to get into orbit. (ok I'm teaching my grandmother to suck eggs-- sorry
but I had to say that just in case)

Keep us posted on how it goes hey
Don

 

[plcdoc]

Hello mate,
try a unit called a voltage sensing relay, these are available in ranges from 0.01 volts to 4 volts dc and will give a relay output to interface with your shaker, the unit i use is made by carlo gavazzy.

let me know if you require any further info

andy