• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Count Down Timer for 20 Minute Parking

Not open for further replies.

Steven Torman

New Member
I have a parking issue at my job, of which I am responsible for finding a solution. I have not been given many resources, but I definitely think my idea should be relatively easy to accomplish.

I have purchased a large display countdown timer for my parking spaces, which are at a 2o minute limit. In order to enforce the time limit, I thought it would be great to have a physical reminder of the countdown to start. My original idea was to have the parking attendants use the remote control, but since we have so many spots, it would require them to be in the booth all the time.

My thought is, I could wire a sensor to the remote control, so that when a car pulls within 3ft of the sensor, it would trigger a switch on the remote to start the timer. And the moment they pull away, another switch to reset or even power down the unit.

Is this feasible? To my mind, the only thing I need to do is remove the remote from its plastic casing, mount it in some sort of water proof box, solder some wires to a controller that is further wired to a two way sensor and viola.

Clearly I have have rudimentary knowledge of this stuff, but based on what I do know about circuit, it seems realistic? Any direction available about parts like maybe an IC that would work or which sensor would be best?

If I get some hits on this, I will post some pictures for further understanding.


Well-Known Member
Most Helpful Member
Looks like an Arduino controller with a ultrasonic sensor is the best point at the moment
this, but I would use something other than ultrasonics because of wind. An infrared proximity sensor should work and could be cheaper as long as you make sure the sun doesn't shine into it, then again dust could be an issue.


Well-Known Member
Most Helpful Member
Do some research. There's a lot of car presence sensors. Briefly: https://www.bannerengineering.com/us/en/products/capabilities/vehicle-detection.html?pageNum=1&#all

One application for parking garages is to count the number of spaces available in the lot and/floor. The sensors I remember looking at use RS485.

With that sort of system, you can go right to the spot and ticket the vehicle.

So, you have a network of sensors and you can tell if a spot is occupied and it works for motorcycles, now what?

What is supposed to happen when the 20 minute limit is up?

Somebody puts a ticket on the vehicle? Handheld cell phone locator app telling what space gets a ticket?


Active Member
Yeah, it all boils down to how you hope to enforce the 20min time limit? Issue a ticket? Charge extra? Track the owner down wherever he/she is?

There is no point in flow control, or counting cars into and out of a floor/lot, how do you hope to police the exact cars that have overstayed with that system?
Similarly its a lot of hassle to put individual bay sensors, although there are A LOT of companies out there who can do that. Ultrasonics are relatively good and used everywhere, but install costs are high, and they can still give false readings and take a lot of effort to get really accurate. Different heights of vehicles, convertibles, glass sunroofs reflect ultrasonic differently, people who just park like idiots, weather conditions, they all throw something extra into the mix.

One option is to have automatic timestamped NPR on entry and exit, if the vehicle hasn't been seen at the exit within 20mins of its entry, then its number plate gets flagged. You can display them on a sign board or whatever.
The other option is nothing new, just like every paid parking lot. Boom gates on entry and exit with a ticket that gets issued, if you have overstayed based on your entry time when you exit you get penalised somehow.

dr pepper

Well-Known Member
Most Helpful Member
A professional way to do this would be to use an inductive vehicle sensor, you bury a wire in the road and the control box will close a relay when a vehicle drives over it, they are used where I work to automatically open doors for mobile plant.
They cost ££'s but are reliable.
You could just stick a 20 minute 555 monostable on the end and it would do the job, or program an arduino, but thats more for an intermediate hobbyist.
If your interested in building a vehicle loop detector chemelec who frequents this forum has published one:
Not open for further replies.

Latest threads

EE World Online Articles