signal delay over phone wire

Discussion in 'General Electronics Chat' started by cjoler, Apr 7, 2010.

  1. cjoler

    Thread Starter New Member

    Apr 7, 2010
    Hello. I'm hoping someone can assist me with an issue that has me saying words that I try very hard not to say. I have a printing press that uses a lot of photoelectric sensors to limit strokes and notify the main controller that the motion is complete. The sensors use standard telephone wires to send signals. I would like to delay a signal when one particular sensor is tripped and was wondering is there is a device/component that is as simple as unplugging one end of the phone cable and inserting it in the middle then reconnecting with a second cable to the original destination? Ideally, it would allow me to vary the delay until I found the ideal value -- 1/2 second to 5 seconds would be plenty. I know very little of electronics and have tried unsuccessfully (with some slightly less amateurish third party help) to control it on the power supply side with no success -- there are six separate boards, among other components, all tied together with lots of logic that requires all motions at six locations to be complete before activating the next step. The particular sensor I want to delay is the one that says "ok - the table is in the right place so start all the motions" so it isn't actually in the middle of potentially interfering signals. Thanks so much in advace for any input!
  2. kkazem

    Active Member

    Jul 23, 2009
    To answer your question as simply as possible, no--there is no simple ckt that you can just plug-in between the sensor and the connecting wires. But, what you want to do can be done without too much trouble, and probably the hardest part would be tapping into your unit's power supply to feed a new circuit that would do the job. Ok, the signal from your sensor, assuming it's already a logic-level signal (and it very well may not be), can feed a simple and inexpensive IC circuit called a 555 timer (T.I. P/N: TLC555CN or equivalent). This IC can use a simple pot (variable resistor knob) to adjust the delay to whatever amount you want from microseconds to several minutes or even more. I don't want to put a damper on your project, but it sounds like you don't have enough electronics knowledge or experience to breadboard this circuit and hook it up. First, you need a scope to see what the input signal to the delay looks like. Then, you need to tap into your unit's power supply or else provide your own separate power supply to the 555 circuit, but you need the information from the scope to know what voltage to use, 5V, 12V, 15V, etc. It could even be 3.3V. Then, the 555 has to be designed as a one-shot (also called a monostable), which simply means that it takes a trigger signal in and gives a delayed signal out. But again, without seeing a scope plot and knowing the voltages and the timing, you are out-of-luck. If you have a friend with a scope who can help you, then great. The 555 timing circuit can largely be designed using an Excel spreadsheet to calculate the values of the timing components for the 555 IC, T.I. provides this free on their website. But you'll need a few more parts than just the timing parts. You'll likely need an input signal conditioner for the 555 ckt, usually just a single resistor and cap, but it has to be designed properly for the timing of your sensor. And it may need an output inverter or other signal conditioner so that the output of the delay circuit will correctly feed the circuit that your sensor now feeds directly. It isn't real complicated, but it isn't for a beginner either.
    Good luck,
    Kamran Kazem
  3. cjoler

    Thread Starter New Member

    Apr 7, 2010
    Thank you greatly for your detailed help! You're correct that I don't have the knowledge to carry this out, but I do comprehend most of it and will have a friend help me give it a go. Thanks again!
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Timers are a standard electrical component, you do not need to build anything.


    They are basically relays with built-in electronics to delay the operation. They have either screw terminals or fit a one of the standard plug-in relay bases.

    Some are designed to have the delay set using a screwdriver, others are panel mounting so you have an external control to adjust them.

    Your local electrical distributor should have some available, or look at RS components or some other online supplier.

    The one you want is an 'ON Delay' timer or a Multifunction type that includes on delay. You need to find what voltage the sensor gives out (likely 24V) and get a matching part.
    Last edited: Apr 8, 2010