In store checkout line with conveyor belt, what makes the belt start and stop moving? I would assume there is a sensor beam at the end that stops it moving when it senses an item.

Although, I remember as a kid looking and seeing a pedal on the back side of the counter for the cashier to use, and a switch to turn it on and off.

So I don’t know if it’s controlled by pedal or automatically by sensor.

Also, some checkouts have another conveyor belt on other side of the scanner, that moves them to bagging area. So I don’t know if that one moves all the time or not.

I’ve seen standard spec grade light switches and pedals used. I haven’t really been paying attention to how they might be controlled recently.

Yeah that’s what I remember seeing many years ago, was light switch style switches with stainless steel plate. I’ve also seen somewhere, a rocker switch somewhere on top of the counter to possibly control the belt.

Toggle switch turns the on and off.  An infrared beam sensor at the end pauses the belt when products reach the end.

The self checkout belts here they have an infra-red beam and sensor at the checkout end of the belt, you can activate it with your hand even! When there is no weight on the belt, it stops. You can push down with your hand and it moves when there is nothing on it. Not sure about the older ones though.

All conveyor belts in checkout lines here in Israel, operates by pedals.

Every one I've seen in Portland operates solely with an infrared sensor. They move until the infrared beam is broken, then pause. After all the groceries have been removed, they move for a little while, then stop. When the cashier wants to start it again, she breaks the beam and it starts moving again.

I forgot about the timeout function.  Stops if nothing happens for a while.  They'll either break the beam or flip the switch off and back on to wake it up.

The standard setup at a Fred Meyer back home is for a front belt, controlled by the cashier from a switch next to the cash drawer.  It has an IR sensor to stop the belt when stuff reaches the end and will time-out if nothing trips the sensor in a certain amount of time.  Maybe 30 seconds or something like that.  If there is a bagger helping, there is a back belt that sends stuff from the cashier to the bagger.  It's controlled by a switch at the bagger station, and it's a simple on/off setup with no IR sensor or time-out.

I've never seen a pedal operated belt before.

I remember an older supermarket that we would go to when I was growing up, either SuperValu or Carrs that either didn't have an on/off switch for the belt, or it was in an inconvenient place, so the cashiers would stop the belt by dropping a separator bar in the path of the IR beam.

As mentioned above most systems use a IR sensor to know when to stop. As for triggering the belt, I've seen momentary buttons on the console, momentary rocker switches, and even foot pedals in some places.

It's also common in discount grocery stores here where you bag your own groceries to have a pair of conveyor belts after the cashier with a customer activated switch for it to bring your groceries to the bagging area. I've seen similar switches used to activate those but never foot pedals, although in some systems the cashier has additional foot pedals to activate the two customer use belts as well. 

Never heard of a belt to the bagging area before, usually there are just rollers or a downward slope here.

It seems to only be a thing in the discount grocery stores. The full service ones typically did not have a second belt since the cashier bagged your groceries.

Anyway here's a typical setup from one of the discount grocery stores here. You can see the pair of belts after the cashier to the bagging area. After paying you had to stand at the end and press the button to activate the belt to bring your groceries over to you. IIRC there's no automatic stop on the second belt and it'll run as long as you hold the button down.

The second belt is paired up to allow two customers to bag their groceries at once.

Wow, cool. The shiny bit just before those belts is where the bagging area usually is here. Do you have self service checkouts which have a full sized belt similar to assisted checkouts in Canada? There is a large Australian grocery chain which converted assisted checkouts to self checkouts in this way.