ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Where is Everyone?
by gfretwell - 11/27/20 06:18 PM
Happy Thanksgiving
by gfretwell - 11/26/20 08:52 PM
Insulated Tools: A Waste of Money?
by HotLine1 - 11/26/20 12:28 PM
Ground fault remover :-)
by NORCAL - 11/26/20 08:13 AM
Work Gloves?
by sabrown - 11/25/20 01:54 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
1 registered members (Scott35), 12 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Photo cell/solenoid control #8384 03/20/02 02:21 PM
Joined: Dec 2001
Posts: 50
Joe Carpenter Offline OP
I have a control setup with a photo eye's output controlling a solenoid valve. This system is set up to control the tracking of a wide sanding belt. this belt ossilates from side to side on it's drums (as it is supposed to do). The photo eye is set up so that when the belt ossilates over so that the photo eye cannot "see" it, it activates the solenoid which activates an air cylinder which sends the belt moving the other way. My problem is, this photo eye does not always read real clear and therefore does not send a solid signal to the solenoid and therefore causes the solenoid to "chatter".
Finally, here's my question: Is there a device available that I can install between the photo eye and the solenoid to "smooth out" the signal the photo eye receives?


Work Gear for Electricians and the Trades
Re: Photo cell/solenoid control #8385 03/20/02 03:31 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
You could put in a timing relay, wired to latch upon the first signal from the photocell. Set the time so that the solenoid will operate long enough to achieve the desired opeation. When the time runs out, timer de-energizes itself & the solenoid.

I use a similar timer for a diesal fuel pump that the truckers just can't seem to turn off. I think it cost around $40 or $50, has selectable time ranges from seconds to minutes to hours.

Maybe someone else has a more elegant solution.

Few things are harder to put up with than the annoyance of a good example.
Re: Photo cell/solenoid control #8386 03/20/02 04:26 PM
Joined: Mar 2002
Posts: 6
stanley Offline
Junior Member
I suggest you should use a micro PLC, you can connect the photo eye's output as an input signal of the PLC and the PLC can control the solenoid valve. the PLC can filter the fake signal of the photo eys (by programing).I suggest you can use the Siemens LOGO!.
you can mail me for more detail infomation.

Re: Photo cell/solenoid control #8387 03/20/02 05:21 PM
Joined: Sep 2001
Posts: 806
NJwirenut Offline
A PLC for a single solenoid valve? That seems like killing a fly with a bazooka, no? smile

A few simpler/cheaper options that might work:

A sharper light source (maybe even a laser diode), to focus the light onto a smaller area of the target.

A corrective lens in the optical path (for the same reason)

A "delay on make" time delay relay or a "one-shot" timer between the photocell and the solenoid.

Use 2 photocells spaced an inch or so apart, and a relay that only fires the solenoid when both of them "agree".

If the output of the photocell is DC, a capacitor hung across the output may provide some "damping". Check this with a scope.

Re: Photo cell/solenoid control #8388 03/20/02 05:52 PM
Joined: Jul 2001
Posts: 599
JBD Offline
I agree with njwirenut, you need to use a one-shot timer. This type of timer takes a momentary or maintained signal and converts it into a timed signal. The output contacts close immediately and then open after the time delay, whether the input is still there or not.

The Seimens Logo is better refered to as a smart relay and not a micro PLC.

For the others,
Smart relays (also available from Square D, GE and AB) have just a few inputs/outputs, several internal timers, and they are programmed from the front like a thermostat or lighting controller.
They are best when you want to use several timers in an application. They sell for only $150 to $180.

Re: Photo cell/solenoid control #8389 03/20/02 07:46 PM
Joined: Feb 2002
Posts: 14
kenrod3020 Offline
a micro switch maybe on each side in suitable inclosure..?

Re: Photo cell/solenoid control #8390 03/20/02 09:52 PM
Joined: Dec 2001
Posts: 50
Joe Carpenter Offline OP
Thanks for the response, This belt cycles back and forth about 60 times a minute. I've also done some more research since I posted. While I liked all the suggestions, My thinking is also as NJwirenut and JBD suggested, the single shot timing relay. Most machines of this type are set up similar to what NJwirenut described with 2 photocells facing each other. I guess this manufacturer decided to cut corners [Linked Image]

Re: Photo cell/solenoid control #8391 03/21/02 07:47 AM
Joined: Aug 2001
Posts: 31
ctolbert Offline

There are 3 basic types of photo-eyes on the market. Through beam, retro-reflective, and diffuse. You always need an emitter and a receiver. Through beam requires two seperate sensors (a seperate emitter and receiver.) Retro-reflective and diffuse have both emitter and receiver onboard the same sensor, the difference is how the reflection or lack of reflection is handled internal to the sensor.

The reason I point this out, is that all sensors are not created equal. You might find that a different type has better accuracy and less bounce without changing anything other than that.

NJ wirenut is right on the money. I would add a redundancy with a second sensor to make an AND gate....i.e. both have to be on.

As far as timers go. Once you add up the amount for timers and the like. A micro-plc might be just as cost effective. Cost's have came down quite a lot over the last few years.


Carl Lee Tolbert
Technical Support
AC Drives
Your source for the most practical automation products at almost-free pricing, delivered by 11 a.m., just by clicking a mouse.
PH: (770)844-4200


2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Posts: 47
Joined: March 2008
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 9
Popular Topics(Views)
272,009 Are you busy
205,897 Re: Forum
193,951 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3