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Author Topic: Relay to Router  (Read 4578 times)

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Relay to Router
« on: May 20, 2006, 08:56:49 PM »
I am slowely getting my 3 axis mill complete.  I am now at the point of hooking my router up to a relay.  I purchased a model number CY3303 relay with the following specs......    120 VAC 25 AMP  3-32 vdc (logic) 3 ma.  I connected everything up to activate from pin #14.  When I activated the spindle from mach 3 no worky on the router.  I measured the voltage across the logic input and found only 1 volt.  I removed the wiring from the relay and then measured the voltage and it came in at 5 volts.  Apparently hooking up to the relay draws too much.  I put a 9 volt battery across the logic connections and the router turned on, scaring the living daylights out of me.  Is there anything I can do with the current relay to make it work or do I need to purchase a different kind?
Re: Relay to Router
« Reply #1 on: May 20, 2006, 10:50:03 PM »
You may have to put on a pull up resistor... OR look into a breakout board.
Fixing problems one post at a time ;)

Re: Relay to Router
« Reply #2 on: May 21, 2006, 08:43:22 PM »
Ditto, Give a 10 ohm 1/4 watt resistor a try on the grnd side of the relay.
Re: Relay to Router
« Reply #3 on: May 22, 2006, 12:20:36 PM »
I am just learning about pullup resistors so I don't fully understand the connection method as suggested.  Do I connect one lead of the resistor to the relay screw and connect the other lead of the resistor to ground?  It would be nice to have a simple schematic of using a pullup resistor on the relay setup.
Re: Relay to Router
« Reply #4 on: May 22, 2006, 01:06:10 PM »
Two Ways: The First might not work if you have the LPT grng to the chassis or if the 5+ can find ground else where, If the spindle is on even when the relay is off then this is prob the case.

Quick Ascii drawing, but basicly you tie 5+ to the lpt pin, thought the relay to the resistor and finally to ground. This should limit the current the lpt pin pulls.

(LPT Pin) --->  (Relay Positive Lug)   (Relay Negitive lug) ---> Resistor ---> Ground


                        Vcc (Of what the relay's coil is rated for)
                              |    __|__
                            Relay   /^\  Diode 1N4002
                             Coil    /---\
                               |        |
          Diode                 | /
          1N4148  4.7K   B |/  C
parallel  >-|>|-+--\/\/\/- -|        NPN Transistor: BC547A or 2N2222A
port data       |              |\  E
pin                +-|<|-+    | V
            1N4148    |       |
parallel  >-------------+---------+
port ground                   |
And more examples @ http://www.smendes.com/el31p/parallel.htm

Offline chad

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Re: Relay to Router
« Reply #5 on: May 22, 2006, 03:11:36 PM »
HI, I would recomend NOT to connect like the first diagram by bcromwell.

If you take 5v and connect it directally to the lpt pin when the pin is told to go low (gnd) it will be a direct short between +5v and gnd inside of your lpt chip. The chances are verry good that that will blast at least that output and probally the whole lpt.

Look at the pic below. This will limit the current in the low state from the +5 to about .005 A. the lpt should be able to sink this without a problem and it should give the ssr enough umph to fire the opto-coupler in the relay. Do not add a resistor on the other side of the relay just tie it directally to gnd. If this doesn't work let us know and we will find you a simple ttl buffer that will drive it.

bcromwell, Sorry to disagree. :)

Re: Relay to Router
« Reply #6 on: May 24, 2006, 01:05:32 AM »
Thank you chad for the simple diagram.  I worked on it for awhile trying to get the router to turn on.  I measured across the relay from the computer logic side and found the volts only a little over 2 volts.  I kept reducing the resistor size (lower ohms) to get a higher voltage across the logic signal, but the router still wouldn't turn on.  I finally switched the wires on the logic side and the router turned on.  I purchased a relay with no writing on it, so I didn't know the polarity mattered on the relay.  I ended up using a 1K ohm resistor and 5volts from the computer power supply.  All is working now and now I am moving onto my limit and home switches.  Thank you!!!!!!!!