automatic driving timer

[m22]

hi what's a cheap way to hack up a driving timer, something that will count how long i spend in my car per day, something i can reset each day.

i'm thinking that the timer should run when the ignition is on, and power is detected through the cigarette lighter.

 

[m22]

by the way if you can think of a cheap 'hack' eg. using a small mechanic alarm clock im happy to look at these options and modifying the voltage input to use a 12v battery to trigger the timer, and maintain accuracy, im happy to consider these ideas too.

 

[KMoffett]

m22,

How about one of those cheap desk clocks that run off a 1.5v AA battery? Replace the battery with a voltage dropping circuit, and attach it to your ignition circuit. See attached. Just reset to 12:00 at the start of each day. Read the hours and minutes...and seconds...off at the end of the day.

Ken

 

[ronsimpson]

Tractors and some big trucks have an hour counter. My counter does not reset but it does count hours/minutes the motor is on. You might try an auto parts web site or a farm tractor site.

 

[m22]

kmoffet,

the circuit you described is good for an output of 1.5v right ? does it matter if the input voltage changes, for example if the alternator changes the input to ~13v.

if the ignition is turned off (when leaving the car) doesnt the timer reset itself? I want the timer to be good until I reset it not until the car is turned off.

 

[m22]

its funny because so far the only way i can think of is to insert a long (4 hour track) into my cd/mp3 player in the car and mute it. when i exit the car the CD will stop.

 

[KMoffett]

m22,

The circuit acts as a 1.5v output regulator. It will handle input voltages from 5v to 25v. The "timer" is just an analog desk clock...if you pull the battery, it stops where it is. If the circuit is hooked up to the ignition circuit that is 12v when the engine is running, and 0v when it isn't, the clock will start and stop with the engine. Set it for 12:00 in the morning, and if the engine runs for 3-1/2 hrs during the day, the clock will read 3:30.

Ken

 

[Brian Hoskins]

If your watch has a stopwatch function you can just start when you're in the vehicle, stop when you exit, then restart when you get back in again. The obvious problem with this idea is that it's reliant upon you remembering to start and stop your watch when you enter or exit the car. But it's a simple solution!

Brian

 

[m22]

I thought of the stopwatch idea but dont think it would be reliable enough. i'd forget and it'd piss me off

i think the circuit is great and i should be able to build it, i might take the diagram to a local electronics shop and see what they can offer to build it.

when you said timer i thought you meant an electronic one that would reset when the battery was out.

 

[KMoffett]

m22,

You might check and see if the accessory outlet (cigerette lighter) in your car goes On and Off with the ignition. It would make it easy to connect the clock circuit to you car.

Ken

 

[m22]

Yes that was the idea - to move the clock to the glove box and hardwire it in series (or is it parallel?) to the cigarette lighter, so that switching the car off would stop the clock!

Now I just need a cheap clock and the parts which im guessing will only cost a few dollars. whats a cheap yet effective way to connect all the parts up, should I use a board?

 

[KMoffett]

Cheap source of clock: Goodwill, Salvation Army, Dollar Stores...
Diodes: Radio Shack 276-1103 (1N4004)
Resistor: Radio Shack 271-1325 (2.2K 1/4W)
Capacitor: Radio Shack 272-1024 (4.7uF/35v)
I substituted an easier to find capacitor, but note that this one is polarized and must be installed with correct orientation.
Modified schematic attached.
What I have done for mounting small regulator circuits, when using a cigarette lighter plugs is get one of the car-charger cords for cellphones, again from Goodwill, and gut it. Install my regulator inside it. Wire that to a dummy battery, to fit in the clock, made of a wood dowel and a couple of small screws.

Ken