# Metered Parking Circuit help

Discussion in 'Homework Help' started by higaki, Sep 19, 2010.

1. ### higaki Thread Starter New Member

Sep 19, 2010
1
0
I'm doing a mini-project for my course.

basically the requirement of this project is to convert the amount of money to the duration of parking.

for example,
Let's say the for 10 cents, the duration of parking would be 10 minutes.

And my problem is, would like to know how to convert the 10 cents into 10 minutes.

So far my idea is by using a few button switches(each switches indicates the amount of money. eg: switch 1 = 10 cents, switch 2 = 50 cents and so on). Once the switch is pressed, i would like it to convert into duration.(my guess would be using a 555 timer)

any idea on how can i do this? i believe this is simple so if anyone count point me in the right direction would be a great help!

thanks!

2. ### Kermit2 AAC Fanatic!

Feb 5, 2010
4,166
1,125
Hint: AC house current is very closely regulated at 60 Hz. 60 pulses per second.

A set of flip flops can be chained together to divide the first one would output a 30Hz signal, chained to the next which would output 15Hz ect ect. Would be complex only in that it would require dozens of flip-flops to count out many minutes of time.

building a long time count RC circuit is simple as well, but accurately timing its charging rate would be rather tedious and involved.

a final logic AND gate function between the timer flipflops and the RC charging/time limit output would signal the end of the count.

Not an easy project without a micro and memory

Apr 5, 2008
18,225
3,480
Hello,

The mains frequency is dependend on where you live.
In the USA it will be 60 Hz.
In most of EUROPE it is 50 Hz, so you need to divide by 50 to get 1 hz (or 1 seconde).

Bertus

4. ### Georacer Moderator

Nov 25, 2009
5,150
1,271
In what form will the amount of money be stored in the circuit?

The mains is a clever idea for a clock. For the 60-step division, I advise two counters in series. One that counts up to 10, and another counting up to 6. That gives 60. But you need to load the amount of money somehow and that depends on the form of storage.