Photo Sensor Voltage

[mdeltat]

Well, I guess I've been exposed!
The specific problem I'm having with this circuit is as follows:
I am attempting to use a PE that is on when light is received. I would like to shut of a motor when the PE is blocked (off) for a predetermined time interval and then return power to the motor as soon as the PE resumes an ON state. The way in which I am trying to do this is by using a 120vac PE that outputs to a OFF Delay Relay which in turn switches the motor power circuit. I'm not sure if the relay will work properly with 120v applied at the switch as opposed to a dry contact. I have attached a drawing depicting how I am currently connected. This is not working.

Thanks for helping out.

 

[milldrone]

mdeltat,

Ahhh! Now I can see some real incompatibility! The Pins (5,6?) on the relay were ment to be dry contact only no external power! First lets see if the relay still works. Hook it up without the photo eye, just the way the manufacturer's drawing indicates. We want just a set of switch contacts (no power) on pins 5 & 6 (if I'm reading the drawing correctly).

If the relay still works then we need to interface the photo eye with an isolating relay. What we need is a "ice cube" relay with 120v coil. Hook up the photo eye to the isolating relay coil leads (pins 2 and 7 if it's an 8 pin octal) and hook up the timer relay to a set of contacts from the isolating relay

 

[mdeltat]

I was afraid of that. Initially I attempted to use an ON delay and the 120v output would've worked fine, however, I mistakenly chose an output ON when "light" sensor. The OFF delay was my solution but now I faced this new problem. This brings me to a question... is there a way to wire a ON delay relay to behave as an OFF delay? Obviously choosing components more carefully is the correct approach but just curious.
Thank you for your guidance.
mdeltat -- Joe

 

[milldrone]

is there a way to wire a ON delay relay to behave as an OFF delay?
mdeltat -- Joe

It depends,

1. Does your off delay relay still function? If so do you have any info on it?
2. Just to be clear. Are we looking for a hard wired solution, no PLC?
3. Another point of clarity. Does the photo eye's output turn off when there is product in front of it? Even if this is the case we can solve this with an extra "isolating" or "interposing" "ice cube" relay. PS. Does the photo eye still work?
4. Budget? Classroom? Job site? Any safety concerns?
5. List of available parts for the project? Any parts that you use some where else that are available?
6. Is this a correct defintion of the project?

I am attempting to use a PE that is on when light is received. I would like to shut of a motor when the PE is blocked (off) for a predetermined time interval and then return power to the motor as soon as the PE resumes an ON state.

What do you want to happen if the photo eye is still blocked after the time is done?

What do you want to happen if the photo eye "blinks" or is blocked momentary but the timer has not timed out?

What do you want to happen if there is a power failure anytime during the cycle?

It appears from "your friends" drawing that the motor is connected directly to the relay is this satisfactory and within the relay's capacity?

 

[mdeltat]

The circuit is designed to operate as a product backup sensor on a conveyor line. The product passes the sensor quickly during normal operation. If the line backs up, the product will remain in front of the sensor (sensor off when blocked) for some time. If the sensor is off for 2 seconds the off delay relay will open the motor power circuit. The ice cube relay idea will work, however, the relay will be cycling very rapidly while the product passes by. Is there perhaps a solid state option that might work quickly and quietly?
Joe

 

[Brian123]

Did your PE work properly (electrically speaking, not in the context of your project) with your On-Delay Relay? If so, I would think that you could simply get the Dark-on model of your PE and connect it to the On-delay relay to do what you want.

Brian

 

[Cameltoe Fancier]

If the line backs up, the product will remain in front of the sensor (sensor off when blocked) for some time.

Can the "line back up" and the sensor not be blocked? If it can then you need to rethink this hard wired request.

If the sensor is off for 2 seconds the off delay relay will open the motor power circuit.

For a hard wired solution you will need a way to get the line started again. like unblocking the sensor.

Is there perhaps a solid state option that might work quickly and quietly?
Joe

If you insist on a hard wired solution and you want to use the photo eye you selected. Use the multi purpose timer relay made by SSAC, TRDU120A2 this is also sold by grainger as 5JJ50. The PDF for this unit is at http://www.ssac.com/catalog/TRDU2AL1.pdf . This unit was made to have 120 volts applied to the initiate switch unlike the Dayton 1EGC3 You will have to pay special attention to the wiring because you don't want to short your photo eye. In the PDF the unit grainger sells is the middle one of the connection diagram. If you look closely you can see the internal jumper that connects pin 2 with pin 6 denoted by the dotted line.

PS. The timer relay contacts may not have the service rating you need.

 

[mdeltat]

Thank You. The circuit currently works as intended, however, I am using the switch leg of the sensor to actuate an ice cube relay which in turn provides the dry contact for the off delay relay. My concern is that the ice cube is cycling too rapidly as product passes. I would like to use a solid-state relay that provides a dry contact in the same way but I'm unsure if this is possible or what relay to use.