Looking for NPN/PNP repeater or splitter 5

[PaulKraemer]

Hi,

I work with continuous web handling equipment on which I use sensors to detect features on a moving web. The feature I want to detect can be gaps between labels, a registration mark, or defects. Regardless of the sensor technology (photosensor, laser, ultrasonic, etc), they usually have either an NPN or a PNP output. I connect the sensor outputs so that they actuate a device like an inline printer or an inspection camera.

Up to this point, I have used a dedicated sensor for each device I want to actuate. It would be very useful if I could actuate two devices with a single sensor. I am wondering if anyone here knows of a high speed device with an input into which I could connect a single NPN or PNP output from a sensor, and that would give me two or more NPN or PNP outputs that I could use to actuate my devices.

If the outputs were triggered at exactly the same time as the input, that would be good. If I had the ability to enter an offset so that output #1 would trigger at the same time as the input, but output #2 would trigger a fixed time interval after the input, that would be even better.

Any suggestions will be greatly appreciated.

Thanks in advance,
Paul

 

[waross]

Solid state relays.

 

[PaulKraemer]

Solid state relays.

Thank you Waross -

I've used SSR's in heating applications where I have a closed loop temperature controller with a switched DC output that switches the SSR coil on and off in short intervals in a time proportioned manner to regulate the power delivered to a resistance heater.

I should have thought that I could use an SSR in this sensor application. The SSR's I've used in heating applications generally just have a single controlled contact that closes immediately when the coil is energized. Have you ever come across an SSR (or an SSR based component) that has two controlled contacts and allows you to specify a time delay before one of the contacts is closed after the coil in energized?

I appreciate your help.

Best regards,
Paul

 

[3DDave]

I think the usual means for this is a PLC.

 

[analogkid2digitalman]

Time delay relays usually come with several programmable operating modes/delay times in both conventional contact and SSR flavors.

-AK2DM

 

[waross]

You may want to "Roll Your Own".
Use your NPN output to drive several PNP devices in pafrallel.
Use some bias and an RC circuit to add a delay.

 

[PaulKraemer]

Thank you Waross, AK2DM, and 3DDave,

All of these suggestions interest me. I didn't have immediate success with google to find a dual contact SSR with time delay capability, but I emailed my main supplier for control components to see if he has a suggestion.

Waross' idea of rolling my own sounds like it would be a very interesting project and learning experience, but I think it is far enough beyond my current ability that I couldn't realistically devote the time it would take me to figure out how to do that.

3DDave's idea of using a PLC might work for me. We have about 10 similar machines in our facility on which this would be very useful. Unfortunately, most of these machines are not PLC controlled, so I'd have to add a control enclosure with a small PLC. The cost of this would be offset by the savings of only needing one sensor to actuate multiple devices instead of requiring a dedicated sensor for each actuated device. Only requiring one sensor in the web path instead of multiple sensors would save me the difficulty of figuring out where to place multiple sensors on a small machine (about the size of an office desk) without interfering with usability. I'll do some calculations based on our maximum web speed and expected delays that would be introduced by PLC processing time to make sure this won't limit our ability to actuate the actuated devices when we need to.

You all have been a big help. I appreciate it!

Best regards,
Paul

 

[waross]

What are your timing restraints?
You may be able to use a mechanical relay.

 

[danw2]

low end stuff is also known as "smart relay"

 

[PaulKraemer]

Thank you Waross and Danw2 for your replies -

My primary application is detecting gaps between labels on a moving web, and using the sensor output to actuate a print head and/or a vision system. I've been told that the line speed range is 10 to 100 ft/min, but most work is done at 20 to 40 ft/min, and that label sizes vary from 2 inches to 6 inches. If I did the math correctly, this makes me believe in the most challenging case (2 inch labels at 100 ft/min), I would be actuating the relay or SSR once every 100 ms. Knowing the process, I sincerely doubt that they have ever done this even with the sensor directly actuating the print head or vision system.

They only run as fast as the controls and product related challenges allow them to. 20 ft/min with 2 inch labels would mean 500 ms per label. 20 ft/min with 6 inch labels would mean 1.5 sec per label. I'll try to dig into some PLC and smart relay specs to get a feel for whether this might be doable. I'll also talk to the operators and find out what they believe the maximum speeds are for the different label sizes when they are actuating the print heads and vision systems - they might tell me something different than management. I'd be surprised if the print heads and vision systems can even react that quickly.

If you have a gut feeling about whether this might be achievable, I would be very interested to get your opinion.

Thanks again,
Paul

 

[waross]

A quick random search found relays with operating voltages of 3VDC or 5VDC and operating times of equal to or less than 6 ms.
Spec sheet.