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By adamthole
I'm a freshmen college student and currently working at a mom & pop grocery store. We are a smaller store, but get a good amount of buisness. However we don't always have an employee at our cash register. We are often in the back and sometimes don't even know someone is up front. My boss hates it when the customer has to wait, so I thought up this idea.

Basically I would have an IR beam up front by the register that when broken would flip a relay. That relay would send out a signal on the "Simple-RF Link" transmitter from spark fun. All of the employess in the store will have a little pager clipped to their belts that will vibrate when the transmitter is transmitting. Once an employee is behind the cash register, they will trip another IR beam that will flip a relay and turn the transmitter back off.

That is the basic idea. It still needs some work though. For instance, if the employee moves around up front, or goes for a price check, etc. the IR beam will be in contact again and everyone's pagers will vibrate. Annoying.

I am currently only familiar with Logic gates, counters, and flip flops. I've been thinking of different ways to get rid of that problem.

Anyway, if anyone has some suggestions on the problem, or perhaps a better way to do the entire thing, let me know.

By gambrose
Instead of using a beam that got broken you could use a ranger module either ir or ultra sonic you can get lots of kits on robotics sites.
You would need a microcontroller though.
By wiml
A passive IR (PIR) detector, the kind used in burglar alarms and motion-sensitive lights, would also be an easy way to detect a customer coming in ... I picked up some of the detectors surplus a while ago, they're easy to use.

I guess there are lots of ways to watch a doorway :-)

The KISS solution would be to have a switch behind the counter, instead of the IR beam, that disables the pagers. That way if the counter guy is just checking a price or whatever they just don't turn the pagers on. Disadvantage is that employees will always be forgetting to turn it on when they go in back.

You could have PIR modules that watch the whole front of the store, plus an IR beam at the doorway, and set it up so that if the store is empty and someone comes in it pages people, but if the store wasn't empty it doesn't page people.
Why don't you hang a bell on the door handle like everyone else? lol
By adamthole
Well nearly three months have passed, and I finally have a working model...kind of. I really wish I would have listened to you guys about the PIR Sensor.

My current set up uses an HT12D/HT12E in combination with the RF-KLP transmitter/receiver from Laipac. I have a laser that shines into a phototransistor. WHen the laser is shining into the phototransistor the transistor keeps pin 10 on the HT12E low. If someone breaks the light beam pin 10 on the HT12E goes high again. I also have a switch that will make pin 10 low all of the time. (this is the on off switch for when the employee is at the cash register).

THe receiver is in a Serpac 110-0I case. it has an on/off switch on the side and a 2.1 mmm power jack on the bottom. I custom made the battery pack (4 AAA 800 maH). WHen pin 20 on the HT12D goes low, it enables a 555 timer that oscillates a vibrating motor on and off.

Everything works great, except the laser is a huge pain to set up. I have to use a mirror to extend the area that it covers and the mirror is very hard to adjust. I currently just have a 1 in. square mirror and tape. Can anyone think of/know of a device that would make the mirror easier to adjust...or should I just find a PIR sensor? I need something that can tilt the mirror with a fair amount of precision and still keep the beam as close to the floor as possible. I make the laser hit the shoe of the person, so the range is as large as possible.

Also, a PIR sensor would only work when something was moving, right? If it stopped moving, it would stop sensing, correct? This would actually make it a poor chase for detecting if someone was waiting at the cash register, or am I missing something?

I'll add some pics soon
By parag0n
whats wrong with a button marked "PRESS FOR SERVICE" attached to a buzzer?
By adamthole
Actually, we find that only rude people use those. If it is a usual, nice customer they will not use it. If they are in a hurry they will come and get us, but they rarely use the bell (we have one).

Besides, surely you all know that my reason behind this is just a matter of learning and knowing that I can build it, right? It's just an added bonus that it will help out the store.
By pittuck
pressure mat?

Would probably be the easiest. Make / get a large pressure mat???