npn/pnp sensors

If the resistor only feeds 0v to terminal 4 then you can bridge it out and use three wire sensor.

yes I can confirm that the resistor only feeds terminal 4
OK, It looks like the original sensor was a simple n-p-n phototransistor, but because base was unconnected (no external bias w.r.t. emitter), it could be used to pull-up the voltage at T6.

For the new sensor, n-p-n output generally used to pull down a node (T6) to 0V in conjunction with a pull-up resistor.

So p-n-p output could be used to pull up a node (T6) to 15V in conjunction with a pull-down resistor - I think this is what you need..

Since you have the p.s.u./relay module apart, can you confirm a pull-down resistor on T6?
well I've atempted to trace terminal 6 the best I can, it leads directly to pin 2 of the socket at the top of the board then the track is obscured by the counter thumb wheels that also has components mounted beneath
and being a double side pcb I've lost track (pardon the pun)
If it helps the resistance reading between T6 and the negative rail when the module is re-assembled is 3.1k
 
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well I've atempted to trace terminal 6 the best I can, it leads directly to pin 2 of the socket at the top of the board

Surely not the mains supply neutral 'pin 2' :?:

If it helps the resistance reading between T6 and the negative rail when the module is re-assembled is 3.1k

Very plausible - a p-n-p output 3-wire sensor's worth a go IMO.

(You could get the n-p-n type to work, but not without modification and a circuit diagram and some faffing around - hardly worth the effort.)
 
well I've atempted to trace terminal 6 the best I can, it leads directly to pin 2 of the socket at the top of the board

Surely not the mains supply neutral 'pin 2' :?:
no mate its a socket that another pcb plugs into when you reassemble it :)

If it helps the resistance reading between T6 and the negative rail when the module is re-assembled is 3.1k

Very plausible - a p-n-p output 3-wire sensor's worth a go IMO.
this is what i'm hoping, a 3 wire PNP sensor connected
modified t4 = 0V> sensor blue
T5=+15V> sensor brown
T6= module input >sensor black
cable sheild> machine earth?
(You could get the n-p-n type to work, but not without modification and a circuit diagram and some faffing around - hardly worth the effort.)

I agree mate I knew I'd made a mistake rushing in and ordering it with out having a detailed look first, but it will be no probs changing it to a PNP type I haven't paid for it yet and I am on good terms with RS
many thanks to you and bernard for your input though, its not often I post on here asking for help!
 
No problem! Best of luck with it - it made a nice change from reading about 2 way-switching problems and cooker circuits. :D
 
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No problem! Best of luck with it - it made a nice change from reading about 2 way-switching problems and cooker circuits. :D
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If the resistor only feeds 0v to terminal 4 then you can bridge it out and use three wire sensor.

Yes from your description it will be a PNP sensor you need.

The original circut of LED lamp and 220 resistor was putting about 60 milli-amps through the LED so provided the new sensor's operating ( supply ) current is less than 60 milli-amps it won't be overloading the power supply.

Ok managed to get to rs today and re-order so plumped for one of these , which is a PNP type with an operating current of 35mA so hopefully we'll be back up and running soon
Matt
 
I hope you remembered to get the lead for it or a matching plug,

Been there when a buyer bought several sensors and assumed the leads came with them. "" If I buy a kettle it comes with the lead "" :D

Only we didn't laugh :( at 9 pm on site and un-able to test and commision.
 

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