Door Sensor Design Suggestions.

[Peter_wadley]

Hello again,

I've been asked again by a local store owner to design a circuit.

He has asked me to create one of those sensors/chimes that indicate when a customer has entered or exited the store.

The door is of standard size.

Immediately I began brainstorming.. however, each of my designs have flaws.. any help would be great..


1) Use a beam of light which customers trip when they walk through..

I cant figure out a good way to accomplish this..

I have a photo transistor.. flaw: the ambient light will cause interfernce.

I have 38khz IR detectors... flaw: I dont think these work under a constant IR beam.

I would use a small mirror to bounce the IR back to the detector for the above designs.. that way I would only need one PCB.

2) Using a peizo (Do you call these PEA-ZO or PIE-ZO) transducer feed through an op-amp into a pic12f675 A/D converter.. The customer would walk on a mat.. the vibrations would trigger the Buzzer to sound.

3) Probably would be the easiest and cheapest..

I would like to attach one of those magnet sensors on the door.. and the microcontroller pcb on the door trim.. when the door is opened the connection would be broken and the buzzer will sound..

I have no idea where I would find the magnet or how they even work.. I would guess that is has to do with inductance.. really would like to try this design..

When i think of this one I immediately think of those cheap bicycle speedometers that use a magnet and sensor to count revolutions.

4) Tell him I cant do it.

I dont think I want to use LRDs since the ambient light of the sun and store lights will interfere..

Thank you for your suggestions

 

[things]

do people have to open the door to get in? if so, no. 3 should work perfectly (they are called reed switches) if it's just a walk through door, maybe you could get one of those $1 red lasers and rig it up, and put the ldr inside a peice of tube to stop ambient light getting in, but only the laser gets inside and hits the ldr.

 

[Peter_wadley]

Hey things,

Thank you for your suggestions.

Ive found the part I need for the 3rd design..

They are called Magnet Switches..

**broken link removed**

The ironic thing is that the man works at this store hahah

I will go tommorow and pick one of these up.. Will be using the PIC12f629 for Buzzer control.

Thank you wiki

Will post pictures once completed for anyone in the future.

 

[things]

inside the little glass tube, there are two flimsy electrodes. when you bring the magnet near it, the electrodes move towards the magnet, but when the do, they touch the other electrode and complete the circuit. pretty simple!

 

[ericgibbs]

You can buy for around £5-£8GBP a PIR with a inbuilt 'ding/dong chime' specially design for just that application.

 

[Gayan Soyza]

Ive found the part I need for the 3rd design..
They are called Magnet Switches..

Magnet switches are mostly used in Windows.But for a Main Door its not a good idea.

maybe you could get one of those $1 red lasers and rig it up, and put the ldr inside a peice of tube to stop ambient light getting in, but only the laser gets inside and hits the ldr.

This method worked well I have tried this.
But when considering long time run this method goes last.

You can buy for around £5-£8GBP a PIR with a inbuilt 'ding/dong chime' specially design for just that application.

This is the ideal solution for this purpose. PIR door sensors now everywhere in the market you can buy that for a cheapy amount.

 

[Nigel Goodwin]

Isn't this all rather over complicated?, the Victorians managed quite well with purely mechanical means - a simple bell near the top of the door that is brushed by the top of the door and goes 'ding' as you open the door. Slighter later, it was replaced by a mechanical switch that the top of the door brushes as it opens, operating an electric bell. You could use the mechanical switch to operate anything you want, including one of those voice recorder chips!.

 

[things]

But when considering long time run this method goes last.

why is the run time short? those lasers should last almost the same amount of time as an led? why isn't a reed switch good for a main door?

 

[Peter_wadley]

Magnet switches are mostly used in Windows.But for a Main Door its not a good idea.

Really? It is working great!

Isn't this all rather over complicated?, the Victorians managed quite well with purely mechanical means - a simple bell near the top of the door that is brushed by the top of the door and goes 'ding' as you open the door. Slighter later, it was replaced by a mechanical switch that the top of the door brushes as it opens, operating an electric bell. You could use the mechanical switch to operate anything you want, including one of those voice recorder chips!.

I bet if the victorians had electronics available at the time, they would do the same thing

why isn't a reed switch good for a main door?

Works perfectly for my door!

Here are some pictures before I give it away.

 

[ericgibbs]

Peter,
A problem I would consider for a 'shop' door, is that many shopkeepers have the shop doors held in the open position,
especially during warm weather.

In that case any door fitted electro-mechanical device would always show a 'door open' condition?

I would suggest an internally fitted PIR/chime would be a good option.

 

[Peter_wadley]

Peter,
A problem I would consider for a 'shop' door, is that many shopkeepers have the shop doors held in the open position,
especially during warm weather.

In that case any door fitted electro-mechanical device would always show a 'door open' condition?

I would suggest an internally fitted PIR/chime would be a good option.

Hi there ericgibbs,

I made sure to ask the customer questions such as this.. He told me that since he runs his air conditioning throughout the summer months his door is is always closed waiting to be opened. (Like all closed doors do )

 

[Peter_wadley]

ARGH

This guy wont give me a break!

I just brought him the reed switch circuit.. all was good and he liked it..

THEN!

He explains it is for his back door! He is using that circuit to monitor his employees entering and leaving the store!

NOW

He wants me to make one of these motion sensing circuits!

Does anyone have any knowledge or schematics of PIR circuits? Are they hard to make?

 

[HarveyH42]

Here's a link to ready built unit on the cheap...

https://www.goldmine-elec-products.com/prodinfo.asp?number=G4567

I got a couple last summer, little cheaper special then. They do work pretty good, and can power a piezo beeper directly. They give good hook-up instructions, clear pictures. There is a 15 second delay between triggers, which kind of killed the idea I was working on, but might be great for what you want. Would be cool to use the built in RF transmitter, but not enough to buy their reciever kit...

Oh, should mention that building a PIR device from scratch sounds complicated to me. There are chips you can buy that do most of the amplifer/timing stuff so maybe not too bad, but you still need to get the lense...

 

[audioguru]

Shops that keep their doors open in freezing and blistering temperatures do a lot more business than shops who close their doors.
People walking by feel the relief of warm or cool air and stop there for a visit.
Then they BUY, BUY and BUY.

 

[Peter_wadley]

Here's a link to ready built unit on the cheap...

https://www.goldmine-elec-products.com/prodinfo.asp?number=G4567

I got a couple last summer, little cheaper special then. They do work pretty good, and can power a piezo beeper directly. They give good hook-up instructions, clear pictures. There is a 15 second delay between triggers, which kind of killed the idea I was working on, but might be great for what you want. Would be cool to use the built in RF transmitter, but not enough to buy their reciever kit...

Oh, should mention that building a PIR device from scratch sounds complicated to me. There are chips you can buy that do most of the amplifer/timing stuff so maybe not too bad, but you still need to get the lense...

Aw that is exactly what I need and at such a good price to!

Fortunately the guy is going to give me one of these:

**broken link removed**

Its ironic that his store sells these!

However he wants a much louder buzzer then this one has.. so Im just going to crack her open and do some enhancing..

Shops that keep their doors open in freezing and blistering temperatures do a lot more business than shops who close their doors."]Shops that keep their doors open in freezing and blistering temperatures do a lot more business than shops who close their doors

I would be more prone to go to a shop that is not wasting energy trying to heat or cool the entire planet!

I few days back I read that parliament is trying to pass a law to ban shops from doing this.. doubt it will pass though.

 

[HarveyH42]

Wow, that's an expensive doorbell... Checking some prices on some other stuff on that site... The Panasonic camera I'm planning on buying soon, is $100 more than the price the manufactuer lists it, and I didn't even check shipping charges...

 

[Peter_wadley]

Yes it is quite terrible, but hey, as long as he is paying heh

Also remember Harvey that the prices are in Canadian Currency.

 

[HarveyH42]

Canadian must have taken a huge dive this past year. Don't think I need to get the actual conversion rate, those prices were way too high. Think I would have gone with enviromentally friendly bell option myself, more reliable...

 

[ericgibbs]

Peter,
I see the 'client' has moved the goalposts, thats very unusual

As its now the back door and not the main customer entrance a magent/reed switch or another electro-mechanical switch would be a cheaper solution.

When you reverse engineer the PIR, lose the ON/OFF switch mounted on top of the PIR also get a 9V WART psu to replace the expensive 9Vbty [PP3 UK].
The psu can also drive the loud buzzer, which should have its own ON/OFF switch.

Lets know how you are going to make it vandal proof, some employee will find a way to screw it up.

 

[Peter_wadley]

Peter,
I see the 'client' has moved the goalposts, thats very unusual

Your being sarcastic right?

As its now the back door and not the main customer entrance a magent/reed switch or another electro-mechanical switch would be a cheaper solution.

When you reverse engineer the PIR, lose the ON/OFF switch mounted on top of the PIR also get a 9V WART psu to replace the expensive 9Vbty [PP3 UK].
The psu can also drive the loud buzzer, which should have its own ON/OFF switch.

Lets know how you are going to make it vandal proof, some employee will find a way to screw it up.

Thank you for the tips!