which relay to use with sensor?

Hello I`m looking to build my own type of motorhome alarm . The plan is to use about 16 car reversing sensor fix it the side skirts of the motorhome . so this will detect people who approach the motorhome at night when im tuck up sleeping inside. I will use the buzzer type without a lcd display but remove the buzzer and just wire that into; The sensor will detect someone outside at about 1.4m Then it will send a pulse signal to buzzer now the relay/headlights.what i want to do is wire from what was the buzzer into a relay that will make the main headlights flash.at this stage. Then as someone get closer say at 400mm the sensors will make a constant signal again to what was the buzzer but now a relay/siren which i want to come on its a voice warning siren again i assume via a relay. The alarm will switch on/off by a remote control key fob My Qestion is what type of relay do i need to be able to pick up the pulsing signal and make the headlights flash? is it simply a flashing relay? Also what type of relay for the constant signal for the siren to come on I think there is a one relay that detects the two signals ? Thanks for any replies

A sensor of that nature will not usually provide enough current output to trigger a relay.  Even if it was able to provide enough current, once they move away from the sensor your siren or buzzer will be silent.  You will have to have some kind of alarm system to use with the sensors.

Thankyou for replying Thats what i want to happen as someone gets close the motorhome the alarm sounds,and then as they walk away it stops. The reason for this is i travel in spain .Within the motorhome world it is known that there is a problem with people trying to break in at night while you are sleeping what they do is use narcotic gas and put in through windows and exhaust pipe to knock you out so they can rob you. So the sensors/detector or warning that someone is approaching is what i need .As i will be inside at night moving around i need an external sensor only. As you say there may not be enough power from the sensor to power a relay.I know one company in the uk use parking sensor as part of a kit but charge over £800 so im sure it works but im sure they wont tell me how. Thankyou The sensor can also be tilted upwards so not to pick up small wildlife.

Thankyou Im not sure if the output is ground or positive is there a way of checking with a ohm meter .I do not have the sensors yet i have ordered them from ebay so i should have it soon ,I then intend to do a mock up with all the pats on a bench,in the uk we call that a bench test Thankyou again

Do you have a datasheet or other information about the sensors? I would imagine they are ultrasonic and that their output is an analog signal not a discreet + or -. There has to be some way to determine sensing distance from the output (voltage, frequency, current, etc). You will most likely need a complete interface circuit (like mentioned above).Kevin Pierson

You've got to bench test (yes the colonials also use that term) and test the output.Open the units up (you will need one for each side) and test the board. It's just occurred to me that most of the reputable back up sensors have buzzers. If these are voltage rather than speakers, you could relay sirens onto those outputs. Test the buzzer on the bench, the buzzer wires to see if it's giving you 12 volts.

Thankyou It nice to know you use the same term as us . The sensors are ultrasonic they are part of a kit you buy which links to a control box which is powered by 12volts.The control box i assume turns that signal into a power output to the buzzer i will check this out when they arrive .If the wire from the control box to the buzzer is showing signs of power .Going back to my original question what type of relay do i need .I want the headlights and indicators to come on flashing .Then the siren as someone gets closer .The sensor give off different buzzing noise ie slow buzz then more rapid buzz this is the detection part at different distances.when you get say about 400mm away from the sensor the noise from the buzzer would be constant its the constant one i want the siern to kick in When i get a data sheet i will add it to the post Thankyou

Unless you can pick up these different noises as voltage I think you're asking the impossible. What is your motor home, Fiat based? You'd be better off installing the alarm, I cant see any way your going to make this parking sensor work, you'd be better off installing something like a Viper and at least a pair of dual zone prox sensors, up to four in fibreglass housings assuming your bodywork is steel at the front and aluminium at the sides and rear. And yes I'm fully aware of what happens in Spain, my sis and brother in law did that trip a couple of years ago nearly hijacked at a Spanish petrol station thankfully I lent them my psycho German Shepherd.

You will need to set the system up and measure the frequency output of the module to the beeper. If you are lucky the output will be discreet and not itself a frequency. If the output is either a switch 12vdc or a switched ground you should be able to correlate a frequency to distance. You can then possibly find a programmable frequency switch that you can set to trigger above the desired setpoint (distance). The problem with this is if they get too close too fast it will go right to constant on, which is not a frequency and thus won't trigger the "warn away". To function with the constant on you can get a time delay on relay and set it to a point greater then the longest beep the module will ever emit. You definitely have your work cut out for you on this one!Kevin Pierson