PIR Troubles

[Blazemaguire]

I have a student in my year 11 electronics class who, is struggling to get his PIR sensor working for his burglar alarm.

The PIR he is using is a 10m long range (black) model:
http://www.rapidonline.com/netalogue/specs/61-1500e.pdf

The PIR is being used as a digital input, is connected to a ~5.5V source, and he is using a 18x chip.
Does anybody know how it is connected/what resistors are needed etc.?

So far, he has tried connecting numerous resistors from the negative leg to 0v, to protect the PIR, ranging from 0-10M ohms. He has also tried connecting the positive leg to negative and the negative to positive as is done with infra-red sensors.

I have used phototransistors + Infra-reds before, but not PIRs.

Should the PIR be treated as an analogue input or digital?

Many thanks

 

[Dippy]

Teacher Blaze: "He has also tried connecting the positive leg to negative and the negative to positive as is done with infra-red sensors."

Not very clever is that? Especially when the Data Sheet you linked gives examples.

Teacher Blaze: "So far, he has tried connecting numerous resistors from the negative leg to 0v, to protect the PIR, ranging from 0-10M ohms."

Eh? Why? This is a sensor with the gubbins built in to make life easy. Don't treat it like a pyro sensor.


The Data sheet shows examples of using it with a transistor. Have you tried any of those?
It's under the section mysteriously marked "How To Use".....


I've used a similar device via an op-amp in the past with a (I'll swear) Stamp. Worked fine.

So, I suggest you try the examples given in Data Sheet suitable modified to go into an input pin on PICAXE. The transistor example looks a piece of cake. Put a 10K res from your digital pin to +V, then take the collector in that EXAMPLE to your digital pin playing safe via 1k0 res. The PICAXE and PIR module should have commoned ground and +5V.

Unless , of course, you've blown it by connecting the wrong way around.

 

[BeanieBots]

I'll second the "blaze".
Reading the datasheet in a little more detail reveals that the output is logic level between 0v and supply with a maximum current load of 100uA.
Thus, direct connection to a PICAXE input should be possible as long as both PIR and PICAXE have the same power supply.
The output is of course a pulse so there is no point expecting to see a rock solid logic level indicating detected or not detected.

 

[Blazemaguire]

Apologies ....

I let my student log in as me to post the thread as his log-on hasn't been approved by PICAXE admin yet

I told him to make it look like a teacher was posting as I have posted on here in the past and diddnt want to look like a retard!

hmmm, diddnt work to well did it!

Sorry!

Anyhow, problem solved now.

Regards

Rob (the real Blaze)