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| DaOld Man:
Most modern autos these days have either a beeper to tell you that you left your headlights on, or they automatically turn off after a few minutes. But older cars probably have neither. Back in the day, I had a 1988 Firebird, which had neither. One night I left the lights on and the next day the battery was dead. So out of necessity, I came up with this extremely simple headlight minder. The hardest part of this is connecting it to your car. I used an small electronic buzzer. The one I used was polarized, if you connected it backwards it would not work, which was just what i needed. I connected it to the radio circuit to get the ACC, and to a parking light "hot" wire, that way it still works if I just leave the parking light on, and if I need the lights on, the alarm is silenced if the key is turned to ACC. If both lights and ACC are on, there is +12vdc to both sides of the buzzer. (Buzzer silent.) If lights are off but ACC is on, the polarity on the buzzer is reversed. (Buzzer silent.) If both are off, there is ground on both sides of the buzzer. (Buzzer silent.) But if the lights are on and the ACC is off, there is +12VDC on the 'buzzer +' and ground (through the accessories) on the 'buzzer -'. Current flows through the buzzer and you are reminded to turn off the lights. Diode is only necessary if the buzzer is not polarized, or if reversing the current on the buzzer might damage it. |
| EightBySix:
Would be good to have a separate forum to collect useful electronics help such as this.... Just saying.... |
| BadMouth:
--- Quote from: EightBySix on March 04, 2013, 02:26:06 pm ---Would be good to have a separate forum to collect useful electronics help such as this.... Just saying.... --- End quote --- This is the right place. The name of the forum was changed to Automated Projects, which is a little better description. It still shows up as mrotate in the list as far as I can see though. :dunno |
| DaOld Man:
Combination lock to open a 2 door garage. |
| DaOld Man:
Very handy and simple timer circuit, using a 555 timer and 4 more parts. I am incorporating this into my serial port drive, to ignore the flashing outputs until PC has had time to boot up. Im using 5 volts for the supply, but I think it can go up to 17 volts. (Check specs on your timer to find out for sure. The electrolytic capacitor will have to be selected by voltage too, good rule of thumb is at least 1.5 times the supply voltage. I used a 220 uf 10 VDC elec. capacitor. For Ra I used a 47K resistor in series with a 500K pot, so I could adjust the time. Time range is around 16 seconds to a little over 2 minutes.) I will post the complete drive circuit when I am finished with it. How it works: When power is applied, pin 3 is low, or connected to ground. The capacitor (C) charges through Ra. When voltage on pins 2 and 6 reach 2/3 of power voltage, pin 3 goes HIGH (+) When power is removed, the capacitor discharges through the 1N4148 diode. (Quicker reset than it would be if it only had Ra to discharge through.) And pin 3 goes low. I sent the guy that owns the website an email asking him for permission to use this, but email was returned as un deliverable. If anyone objects to me using this, please let me know and I will remove it ASAP. Here is a link to the site, it also has a handy calculator that allows you to choose the proper values for C and Ra, based on the time delay you need. http://clarkson63.uk/555-timer/operation/frames3.html |
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