Unicom PIR Detector Model No:- 56775

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Tim036

Member
Good news !

Just the job !

runs on 4x1.5V AA batteries with little switch down = A for automatic.

Day/night sensor on a blue wire just cut the wire and its disabled, Its mounted in with the leds.

A 25 second on cycle so a Pic will need adding to get the delay you need.

Taking the case apart needs two screws removing one hidden under a small selfadhesive label.

The PCB is 2 inches by 2.5 inches and even has 4 little screw holes drilled in it. A small posi type headed watchmakers screwdriver is needed.

All that is needed is to run it on +5V lab supply and see if its happy !

I have photos if requested.

This is as good as it gets ! Brilliant.

From Maplin , 2 cost £18.97 from Maplin N98FY Also Uni-Com are based in Edenbridge Kent TN8 6EW

: )))

Tim

Update

With +5v volts applied it draws 30mA when the leds are on, 29.6mA going to the leds from the 4.09volts which it offers to the leds.

With the leds off it seems to use very little current - between 0.4mA to 4mA

Is 4.09 V ok for a Pic 'logic '1' ? What is the threshold here? I'm a bit rusty on the detail.
 
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A

Andrew Cowan

Senior Member
What PIC are you using?

TTL ( Vsupply > 4.5V )

Vih : >= 2.0V
Vil : <= 0.8V


Schmitt Trigger (ST)

Vih : >= 0.8 * Vsupply ( >= 4V @ 5V )
Vil : <= 0.2 * Vsupply ( <= 1V @ 5V )

Therefore, 4V will be OK.

A
 
T

Tim036

Member
Andrew Cowan said:
What PIC are you using?

TTL ( Vsupply > 4.5V )

Vih : >= 2.0V
Vil : <= 0.8V


Schmitt Trigger (ST)

Vih : >= 0.8 * Vsupply ( >= 4V @ 5V )
Vil : <= 0.2 * Vsupply ( <= 1V @ 5V )

Therefore, 4V will be OK.

A
Click to expand...
16F88 is the Pic I will be using.

Many thanks for the responses on Logic levels !

: )

Tim
 
D

Dippy

Moderator
Rusty?
Manual 1. Currently page 7. "At a glance - specifications:"

Though what the manual omits is whether you use STor TTL and the supply voltage.

To save me typing as I am equally rusty, check out your PIC spec from the Microchip Data Sheet, usually under the DC Characteristics heading.
Then check which pin you are using against listing ALSO in PIC Data Sheet.
Bob's yer Uncle.

Example...
 

Attachments

M

MFB

Senior Member
video trigger

I hacked one of these devices a while back and its now triggering a camera to automatically video wildlife in my garden (even recorded a dear early this morning).

For this role, the following mods were required:

a) The photocell and associated resistor had to be swap positions in order to inhibit operation when it is too dark for the (non-IR) camera.

b) The LEDs were replaced by a 10K pull-down resistor and the top of this resistor taken to the digital input of a 08M, that’s used to sequence the camera power-up and record inputs.

All seems to work well but range is limited to a few metres and occasional false triggers are a problem.
 
hippy

hippy

Ex-Staff (retired)
They look like good finds. If current is 4mA rising to 30mA with the LED's on, that suggests about 15mA per LED, and (guessing ) each LED has a current limiting resistor of 150R. It should be possible to add an extra resistor in series with the LED to reduce current and still be bright enough to see. I tend to use 1K8 with the 3mm red LED's I have which is just 2.5mA and they are bright enough for me.

You could just snip the LED's off but if useful for diagnostics, a balance between some current draw and dim output should be acceptable.
 
T

tiiiim

Member
Further to everyone else's posts, just thought I'd share my experience with the Maplin PIR sensors (http://www.maplin.co.uk/Module.aspx?ModuleNo=223593).

I've included images below of the inside of the thing for those interested. The first three are without modifications, the last one with some of my own wires.

I noticed someone earlier mentioned that they used a 10K resistor at the input to the picaxe (from the LED output) - well this certainly didn't work for me. The output at the LEDs (I'm still using the LEDs inside the sensor, in addition to feeding a picaxe) is around 3.9V for me (driven by a 7805 so 5V). I'm using a 2K1 resistor at the input, as using a 10K just didn't register with the picaxe - hope I'm not putting anything in danger as a result!

Otherwise, this works like a charm - managed to hook it up to the picaxe with no problems. The blue wire which was mentioned as hooking up to the LDR (for auto dusk/dawn identification) is clearly visible towards the top of the product.

I found the LEDs remained active for about 40 seconds (very roughly - wasn't timing properly).

Just realised I never checked the current draw by this thing - perhaps I'll have to think about adding a heatsink to the 7805 after all. As they're only LEDs I'm assuming the draw won't be too much, but could this affect the picaxe (which is powered from the same power rail....)

EDIT: when the unit is powered on and in AUTO mode, the LEDs will switch on as if the PIR has detected something, whether or not it actually has. They will switch off again after about 40 seconds - perhaps some sort of "yes, I'm working" indication.

EDIT2: the range and sensitivity of this thing is just phenomenal: +10 metres I got, which for such a diddy cheap thing I thought was pretty good!

Images below (inline cos I can only attach 2 at a time...):

Image 1: the main PCB


Image 2: the inside of the entire unit. The section on the left attaches to the LEDs and LDR.


Image 3: side view showing the switch positions ON/OFF/AUTO


Image 4: my modification - resistor attached to +ve LED output and wires attached to power rail, very easy to solder.
 
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M

MFB

Senior Member
The reason that a 10K pull-down worked for me was that I had removed the LEDs to save power and not frighten the deer that was being videoed.
 
T

tiiiim

Member
MFB said:
The reason that a 10K pull-down worked for me was that I had removed the LEDs to save power and not frighten the deer that was being videoed.
Click to expand...
Ah, cool, I see. In my application I actually want to scare off anything which comes close, hence still using the LEDs! Thanks for that info though!!
 
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Haku

Senior Member
I got one of those Unicom sensors a while back, accidentally fried the main chip (I know, sometimes I shouldn't be let near things with a multimeter & soldering iron :D) but recently my local Home Bargains shop was selling some 4x AA battery PIR sensors for £2.99 each! so I bought 6 :D

Oddly they use a filament bulb instead of LEDs, and include a spare bulb!

I cut the wires to the bulb on one and connected it directly into an 08M (with a pulldown resistor), works a charm, just wish the sensor had more sensitivity as there's no dials for lamp shine time & sensor sensitivity.
 
slimplynth

slimplynth

Senior Member
Aldi have some similar remote controlled Mini Alarms for a tenner, got one after ruining the same maplins unicom motion sensor in the pictures above, though I think the cause of death was being in a vunerable state in the car boot for so long... contemplating changing username to HalfDonePlynth
 
M

MFB

Senior Member
PIR to Video Recorder Interface

On the subject of hacking cheap gadgets from Maplin, I found it quite easy to control one of their basic SD card video recorders using an 08M. On receipt of a trigger from the PIR the PICAXE sent a ‘power-up’ pulse followed by a delayed ‘record’ pulse. These two outputs were wired across the associated push button via open collector transistors, which still allowed manual operation. I think the video recorder was called a Buzzbee or something but it’s probably discontinued anyway. However, there are probably many similar products around that can be modified using the same approach.
 
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