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Author Topic: Wiring of 2 wire proximity switch  (Read 14328 times)

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Re: Wiring of 2 wire proximity switch
« Reply #10 on: May 30, 2010, 07:53:23 PM »
No, it only blows the resistor on the simulation, I haven't built the prototype yet. I'll see how accurate the sim is tomorrow when I put it together  :-[

...Sweep
Re: Wiring of 2 wire proximity switch
« Reply #11 on: May 31, 2010, 11:38:52 AM »
My Denford Easimill used those weird prox sensors.  I couldn't figure out how to make them work, so I cheated.  I cut out the chunk of the original Denford board that controlled them and wired THAT to my breakout board.  Here is an early picture once I got it working, it's not as ugly now.  The board in the lower right corner is the chunk of original Denford board, the diagonal row of transistors and resistors are what actually control the sensors.

cheers,
c



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Re: Wiring of 2 wire proximity switch
« Reply #12 on: June 01, 2010, 03:52:23 AM »
That's also my last resort Vandal968  :D
I cut mine out a while ago and kept it just in case I couldn't figure out how to do it any other way. If the new board works i'll post a reply on here along with the final draft of the circuit. If not i'll probably be asking you a few more questions!

Thanks ...Sweep

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Re: Wiring of 2 wire proximity switch
« Reply #13 on: June 01, 2010, 05:26:21 PM »
I built the circuit earlier tonight but the 82R resistor got very hot and started to smell like it was losing the will to live.
I had taken the precaution of fitting a 1amp fuse, the smallest rating I had, as I was wiring directly to a spare 6amp/hr 12v battery from an alarm system.
I switched off the supply and checked the fuse which was ok and checked the resistance of the 82R which measuered ok.
I then tried again but the same happened, that is the heat and the smell, so I gave up. Whilst the supply was on I did try to detect the 9V but couldn't get a reading.
So, considering that the simulation highlighted this issue, how does a tiny little resistor hold back the pressure of the battery and, if this is a problem, how do I limit potential high currents that might damage some of my components. Ok, my supply is never likely to have the capacity to deliver current like a battery but i'm still curious about the logic.
This is probably a pretty rudimentary question to all you with electronics experience but I am trying to learn as i'm doing the project.

thanks ...Sweep
Re: Wiring of 2 wire proximity switch
« Reply #14 on: June 01, 2010, 05:50:24 PM »
Sweep,
I don't know if this is related or not, but....  See that blue component above and to the right of the transistors in the picture I posted?  When I first hooked up this circuit, that thing got hot, real hot, singed the pc board hot.  A friend of mine who's an EE took a look and said that he didn't see a need for that component, so I snipped it off and problem solved.  I don't know if that component was related to what you're talking about, but I thought I'd mention it.

cheers,
c
Re: Wiring of 2 wire proximity switch
« Reply #15 on: June 01, 2010, 06:43:51 PM »
That appears to be a tantalum capacitor, they are very averse to AC or a high DC ripple and over voltage.
Nosmo.

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Re: Wiring of 2 wire proximity switch
« Reply #16 on: June 04, 2010, 04:51:12 PM »
ok, back to the project...
I think I have figured why I keep blowing the 82R on the simulation when the switch is already closed. Maybe it's because I have the simulation set up with a SPST mechanical switch instead of the correct proximity switch, but what blows the 82R is charging the 10uf capacitor taking the power over the rated spec of the 82R.
Now I can cure the blowin of the 82R by dropping the capacitance of the 10uf down to 1uf but i'm not sure of the effect on the rest of the circuit.

...Sweep