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Beginner needs help

tashman

New Member
Hi Folks, I've just joined looking for help on an electronic timer circuit for indication of when my garage door is being opened and closed. I am a complete novice on electronics, retired now aged 81, been working for 47 years as an aircraft engine man from Meteors to Concorde. Always loved electronics and have built a few kits like a treasure tracer, electronic ignition timer (years back). My problems is I have fitted a M/S to the garage door run from a 12V supply to a light in my hallway together with a noise maker(old battery operated toy from my sons bike years ago) - trouble is they operate all the time. I purchased a Vellman MK111 adjustable interval timer to see if this would do the job. First is this going to be robust enough for the garage door operations, next not sure how I would wire the units up such that the noise operate for a short whereas the light needs to be on all the time the door is open. I would also like the noise to operate on closing but for a shorter time. Am I asking to much or is there a simpler way?
 

AnalogKid

Well-Known Member
Most Helpful Member
With only one switch you can detect one of three things:

1. Door is fully closed - Switch is placed where the top of the door closes against the frame.
2. Door is fully open - Switch is positioned at the end of the track where the top of the door stops when fully open.
3. Door is in motion. - Switch is positioned in the middle of the track and a bump on the door activates it as it moves by in either direction.

Which do you have now?

Moving on, you have:

1. A 12 Vdc power supply. What is it's output current rating?
2. A 12 V light. What is its power rating / current draw?
3. A noise maker. How much current does it draw?

My read of your post is that you want the light and sound to activate for a short time when opening and a shorter time when closing. If this is correct, you will need at least one more switch so the system can determine direction. Yes, you could just have the system toggle between short and long with each activation of only one switch, but this is not as reliable. Things are bound to get out of sync sometime.

With one switch at the open position and one at the closed position, two 555 circuits will do what you want. But where's the fun in that? With two switches placed close together in the middle of the track, only one 555 circuit is needed; it would operate like this:

Switch A triggers the 555 every time it is hit by the door going in either direction. The 555 is set for the long alarm time.

Switch B resets the 555. In one direction it resets the 555 before it is triggered, and has no effect on the 555 output period. In the other direction, it resets the 555 shortly after it is triggered, terminating the output pulse early. This is the short alarm that indicates closing. The distance between the two switches sets the short alarm time.

One simple 555 monostable circuit gets you two alarm times without a bunch of direction logic. Depending on the operating currents of the light and sounder, the 555 might be able to drive them directly. If not, then a small power transistor or relay is needed.

ak
 
Last edited:

gophert

Well-Known Member
Most Helpful Member
Assuming your garage door opener has an integrated light that stays on for a minute or three during and after a door movement. You could use a light activated switch to sense the light rather than trying to sense the door movement.
 

tashman

New Member
With only one switch you can detect one of three things:

1. Door is fully closed - Switch is placed where the top of the door closes against the frame.
2. Door is fully open - Switch is positioned at the end of the track where the top of the door stops when fully open.
3. Door is in motion. - Switch is positioned in the middle of the track and a bump on the door activates it as it moves by in either direction.

Which do you have now?

Moving on, you have:

1. A 12 Vdc power supply. What is it's output current rating?
2. A 12 V light. What is its power rating / current draw?
3. A noise maker. How much current does it draw?

My read of your post is that you want the light and sound to activate for a short time when opening and a shorter time when closing. If this is correct, you will need at least one more switch so the system can determine direction. Yes, you could just have the system toggle between short and long with each activation of only one switch, but this is not as reliable. Things are bound to get out of sync sometime.

With one switch at the open position and one at the closed position, two 555 circuits will do what you want. But where's the fun in that? With two switches placed close together in the middle of the track, only one 555 circuit is needed; it would operate like this:

Switch A triggers the 555 every time it is hit by the door going in either direction. The 555 is set for the long alarm time.

Switch B resets the 555. In one direction it resets the 555 before it is triggered, and has no effect on the 555 output period. In the other direction, it resets the 555 shortly after it is triggered, terminating the output pulse early. This is the short alarm that indicates closing. The distance between the two switches sets the short alarm time.

One simple 555 monostable circuit gets you two alarm times without a bunch of direction logic. Depending on the operating currents of the light and sounder, the 555 might be able to drive them directly. If not, then a small power transistor or relay is needed.

ak
 

tashman

New Member
Thanks for your reply. My microswitch is supplied by 12 v and when operated lights up a 12v car sidelight bulb (could now be a LED) and also the noise buzzer toy which use to run of a battery (think 3v)
I do not want a complicated circuit, just one I can understand with my limited knowledge. I could use other microswitches to turn on the light just that I need the noise to last say 5 secs on opening and just 2 sec on closing. Something to give me an indication of open or closing.
 

AnalogKid

Well-Known Member
Most Helpful Member
The most simple thing I can see is two 555 timer modules from ebay for about $3, and two switches, one at each end of door travel. One module is set for 5 seconds and the other for 3 seconds. Both sets of relay contacts drive both devices in parallel.

Zero soldering, all purchased assemblies, nothing but field wiring. I'll see if I can sketch this later.

Does your microswitch have two terminals (SPST) or three (SPDT)?

ak
 

AnalogKid

Well-Known Member
Most Helpful Member
First pass at a no-soldering solution. When the door is stationary at either end of its travel, that switch's normally closed contacts are open. When the door moves, the normally-closed contacts close and trigger the module.

Note - the relay symbol is what's in my design library; ignore the part number.

ak
Garage-Alarm-1-c.gif
 

shokjok

Member
Have you considered a tone generator or LEDs to indicate the active door's direction? I suggest connecting momentary switches to a timed power supply, then connecting the timer to the indicators and a bidirectional motor driver circuit. Stop switches, and panic buttons, would disconnect the timed power supply, hibernating the pirate circuit.
 

shokjok

Member
The tone generator emits a high or low tone for a door opening or closing, respectively. The timed power supply could be a relay/ resistor/ capacitor combination similar to an auto flasher, while bidirectional motor driver circuits can be found online. You'd only want this circuit operating when you need a garage door action, not draining your wallet for consumption costs like clocks, fridges, etc. .
 

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