Trouble Triggering 555 Timer

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Thread Starter


Joined May 8, 2015
Hi, total newbie to this site - hoping that I can get some assistance with a project I'm working on.

Modern convertible vehicles have a device that drops the window 10mm when you open the door and raises it to the seal when you close it. I own an older convertible car which does not have this capability and therefore, the windows don't always seal correctly. When I was much younger I used to make simple electronic gadgets therefore, I thought I'd make a 'window drop module'.

Attached is the schematic that I have designed - I'm sure it's not very elegant so please be gentle..... I have tried to simulate the design on easyEDA but it doesn't appear to work. Before I blew the dust off my breadboard and invested in components I thought I'd try out this site for help.

In short, my circuit is built around two 555 timer chips. The hope is that these will provide me with an output for a set duration upon triggering. Presets R1 & R2 would be used to fine tune these durations.

The 555 on the left (labelled IC2) controls the drop of the window. When the existing door switch (used to switch the internal lights) closes it goes to ground triggering the 555 to provide an output to relays 2 & 4 for 0.5 seconds. This will be long enough for the window to drop approx 10mm.

The 555 on the right (labelled IC1) controls the lift of the window. When the door is closed the door switch opens causing (I believe) current to flow from Collector to Emitter in TR1. This will trigger the 555 to put an output of 1.5 seconds to relays 1 & 3. This duration is longer than the drop signal as it needs to ensure the window is pressed against the seal. I have added R3 & C3 in an attempt to delay the lifting action to ensure the door is fully closed, This will ensure that the window won't start to lift before the door is completely closed.

SW1 is a reed switch that will be fitted inside the door to disable the device if the window is already down when the door is opened or closed.

The fuses are existing within the car and are primarily there to assist my integration into the car - assuming that I can progress the project that far.

As I said, it's been a long time since I last played with any electronics so I'm guessing there is a much simpler way to achieve my goal but I have hit the limits of my knowledge now. Any help or guidance would be very gratefully received.

Many thanks,




Joined Aug 23, 2012
Welcome to the AAC forum.

The owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

This thread is against the AAC forum rules, Terms of Service (ToS).

Any kind of over-unity devices and systems
Automotive modifications
Devices designed to electrocute or shock another person
LEDs to mains
Phone jammers
Rail guns and high-energy projectile devices
Transformer-less power supplies
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Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

Please try to understand the reasons behind this action, and feel free to browse and use the forums.

You might find answers to your questions in one of these forums:

Another good forum that shares many of the same membership is .

Good luck.
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