Mobile Phone Detector

[mildenhall]

This is a mobile phone sensor I build for my Y8s (12-13 year olds). It fits nicely onto a circular PCB.

The BC547 does most of the work, and the PIC is just used to control the sensitivity, and how the circuit responds to being triggered.

Before you ask, I desided the 3.5mm jack socket was too complicated for Y8s to solder, so used a tripple terminal block instead.

'*** Mobile Phone Detector
'*** (c) Jerry Davis, 2009
'*** King Edward VII Technoloy College
'*** Melton Mowbray, LE13 1DR, UK

'#define SHOWDEBUG					'comment out to stop the debug screen

symbol ANALOGUE_DATUM = 65			'preset analogue datum value
symbol DIFFERENCE_TRIGGER = 30		'value above datum that will cause a trigger

							'depending on the phone make, model and environment
							'the above two vlaues may need to be modified to suit
							
main:
	readadc 1, b1				'read current analoue value

	if b1 > ANALOGUE_DATUM then		'if b1 is greater than b0...
		b2 = b1 - ANALOGUE_DATUM	'subtract b0 from b1 and store the difference in b2
	else
		b2 = 0				'otherwise b2 = 0 to stop it going negative
	endif

#ifdef SHOWDEBUG
	debug
#endif

	if b2 > DIFFERENCE_TRIGGER then	'if the analogue difference is greater than 27
		for b4 = 0 to 9
			high 0
			pause 200
			low 0
			high 2
			pause 200
			low 2
			high 4
			pause 200
			low 4
		next b4
	endif
	
#ifndef SHOWDEBUG
	nap 0						'power save nap	
#endif						'when debugging, nap slows the program
							'so the #ifndef removes it if debugging

	goto main

 

[mildenhall]

PCB and layout.

 

[Andrew Cowan]

Very interesting. A couple of questions:
- How do you cut a circular PCB (my answer would be slowly).
- What's the range?

A nice bit of work!

 

[Dippy]

Very nice.
I see they are CAD produced images, have you built a proper version?
Could be very useful. Well done.

 

[Andrew Cowan]

Just noticed - the components and traces are on the same side. How do you plan to solder the terminal blocks/battery holder?

I assume the LED is not flush with the board, so you can put some solder at the legs.

A

 

[nbw]

That's a pretty whizzy project. I'm interested to know the range it has too. Well done!

 

[mildenhall]

Very interesting. A couple of questions:
- How do you cut a circular PCB (my answer would be slowly).
- What's the range?

A nice bit of work!

Sorry for the delay - cut it square,and then use a disc sander!!

 

[mildenhall]

That's a pretty whizzy project. I'm interested to know the range it has too. Well done!

About 20cm

 

[mildenhall]

Just noticed - the components and traces are on the same side. How do you plan to solder the terminal blocks/battery holder?

I assume the LED is not flush with the board, so you can put some solder at the legs.

A

I'm note sure what you mean about the terminal blocks and battery.

I laser cut a coil former, LED spacers to make them proud of the PCB and turn it into a finished product. I can supply images if needed.

 

[Andrew Cowan]

So I take it that the solder/copper side is not the same as the component side? That was the impression I got from your second picture.

 

[hippy]

I can see what you mean; I think you have to imagine it placed on a lightbox with illumination through the PCB.

 

[Andrew Cowan]

Ah - that makes the reverse text make sense too .

 

[mildenhall]

So I take it that the solder/copper side is not the same as the component side? That was the impression I got from your second picture.

Correct. It's just a view that the CircuitWizard software produced. It helps the kids understand where to put the components.