Proximity sensors series setup 12v DC

[MoatRman]

Hi, I hope this is a simple request. I have a towable cherry picker which had fitted a proximity sensor on each outrigger presumably to stop the use of the machine unless all 4 stabiliser legs are fully extended and the sprung metal plate on each became close to the sensor.
This American made machine has been modified over the years. I believe it was battery driven originally. It now has a 6.5 hp engine which can be started by hand pull or starter motor from a 12v car battery. The sensors are all useless as the wiring has broken and one or two badly corroded. The wiring must have been changed as it can be started without the outriggers being in place which for safety purposes and hiring to the general public is not acceptable.
Ok so what I want to do is replace the prox sensors with 3 wire PNP NO sensors and fit an LED green light on the control panel next to the start and stop buttons, all wired so that all 4 must have made contact to illuminate the LED.
I have tried setting up on a bench with 12v battery wired in accordance to various diagrams that are available but cannot get them working. It seems there should be a diode or something in the circuit but I do not have a clue what size etc.
The sensors I have are Autonics PS17-5DP +DC12-24v Brn-(DC 10-30v) Blk-OUT Blu-0V.
Can anyone Help?

[nicholasdark]

I'm still digesting this post a little and haven't had a chance to look for a datasheet yet but I'm wondering if 4 reed relays wired in series might do the job.
Something like this maybe?

http://uk.rs-online.com/web/c/relays/re ... r=asc&pn=1

If you were to drive the coil of each relay with the output of the sensor, then you could wire the contacts from each relay in series with each other and the LED. That way the LED would only light when all four relays have been energised.

Kind regards
Nick

[nicholasdark]

On a related note, while you are in there modifying the wiring, it might be nice to add an LED on the output of each Prox sensor and mount them on the control panel as well. That way you can see if one isn't set properly.

I used to have lots of fun running around a man lift trying to work out which leg wasn't tripping it's interlock despite them all being sat firming on the ground.

Kind regards
Nick

[MoatRman]

Thanks Nick, but the sensors I have purchased have there own led already built in. I thought reed relays require there own magnetic counterpart and as my machine has a sprung loaded plate there is no way to fit them.
As the prox sensors that I have are shielded and sealed the only connections are to the 3 wires each of them have.
I thought that by connecting the power to the 1st sensor and when activated the switched wire would then connect to the next sensor and so on I would get a circuit but I really don't know what to do with the 3rd wire from each sensor or if I should add anything else. I am still baffled as every configuration of connections do not allow all sensors to be activated with each of them having there own led lit plus the separate led that I want on the control panel.

Hope you can help a little further.

Regards Tony

[nicholasdark]

Hi Tony,
Ah so much for my bright ideas haha.

I think you are confusing reed relays with reed switches. A reed switch as you suggested does indeed need a magnet to operate it. A reed relay however is effectively a reed switch with a coil of wire wrapped around it. When you energise the coil it creates an electromagnet that activates the switch.

The key advantage of a reed relay over a normal one is that they normally require much less current through the coil to activate them.

Kind regards
Nick