Uni project

[vivalefrench]

Hi all.

For my university project I am making a simple heron/cat deterent for a garden fishpond. (A sensor detects the pests and fires water)
I have a P.I.R Sensor with a built in relay, and I have a 12V water pump out of a car windscreen washer system.

The pump and sensor work fine. My problem is getting the pump to work when the P.I.R Sensor detects something.

I have wired the pump to a 12v battery which is connected to the built in relay of the P.I.R sensor. I can hear the relay clicking but the pump doesnt start. I was advised I may need another relay. Can someone suggest what relay I need and where I could get one from?

Info
On the P.I.R. sensor leaflet is says:
Relay output: 0.2A/28V with 15ohm resistor

 

[breezer]

you need a 12v dc relay, get one form maplin

however you have a few other problems to overcome

1)a pir relay is normaly closed going open in alarm, but using another relay will solve that problem.

2)you should be aware an intruder alarm pir (as you appear to have) does not stay in alarm for very long you will probably need a timer (even if only for a couple of seconds)

3) Your windscreen washer pump will also need the washer jet other wise the water will not go that far (it wont go THAT far anyway

4) your jet will be in a fixed position so it may miss any "animals" the "thing" you are trying to copy actualy has a water sprinlker, the type that sends out a jet and is moved by a mechanical warm which is powered by water pressure

5) good luck

 

[vivalefrench]

Thanks for the reply breezer.

Ok, I will have to get a 12v DC relay. How could I use two relays to invert it- if it was closed-going open?
Should I buy two 12v DC relays just incase?
I went to a scrap yard and got the pump with some hose and two jets. I have tested the pump and am moderately happy with the pressure.


I have seen the existing one of these things that uses the pressure from the mains to shoot the water. Its excellent. When I write my report my argument is going to be that the unit costs £60 (which I think is a lot), and you will have to dedicate an external tap to it.

 

[breezer]

you only need one relay (12v dc coil) as the pir already has one

 

[Pat-UK]

You could make a small circuit that incorporated a Transistor and a timer and use the signal that goes to the PIR relay to activact the transistor which in turn would switch on the Pump for the pre determind time.

if you need any help on this, give me a shout.

 

[skybluescooby]

and you will have to dedicate an external tap to it.

Why not run the feed from the pond itself, so no chlorinated water finds its way back to the pond in turn reducing the possibility of harming the fish

 

[vivalefrench]

Thankyou for the replys everyone. I have taken some pictures of what I have to help you to help me
Please find the pictures below:


This is a picture of the instructions/spec leaflet that came with the PIR sensor:


This is what the PIR sensor looks like:


This shows the PIR sensor with the cover taken off, exposing the circuitry:


This is a close up of the circuitry- showing the terminals etc:


This shows the 12v windscreen washer water pump taken from a car:



Is there a simple way to connect these components as I am new to electronics like this, despite doing an engineering degree.

 

[breezer]

you still need a 12v relay, the pir is closed going open

 

[vivalefrench]

Sorry, I got this too (12v DV relay as you said) forgot to take a pic, here it is:



Even if the pir was closed going open, the pump should still work when the sensor isnt detecting anything....but it isnt. I cant get it working.
(The pump works fine on its own but not when connected to the sensor relay)

 

[breezer]

from the picture that one is not suitable, can you turn it over and take a picture of the otherside?

you need a relay with contacts going closed when coil enegrgised (or change over) that one looks like going open on coil energised

or better still get this the 12v one

 

[vivalefrench]

That makes sense. I see exactly what you mean. Any ideas to why the pump doesnt work when rigged to the pir relay though? (it should still come on when the pir sensor isnt detecting anything)

 

[breezer]

the pir probably has an internal resistor in series with the contacts (its quite common) to stop the contacts "wearing out" becuse of too much current going through them