555 timer question & Bounceless Garage door opener.

In summary, the conversation discusses the issue of needing to push the garage door opener button multiple times when beyond the range of the transmitter. The solution involves using a "bounceless" switch with a 555 timer and a relay to interrupt the signal and prevent multiple open signals from being received by the motor. The voltage requirements of the components and available voltage sources are also mentioned, with the question of whether powering both the chip and relay with a 17 VDC source is safe. It is suggested to use a lower voltage for the 555 and to use a protection diode for the relay. There is also a question about whether the switch would work with an older garage door opener.
  • #1
flatmaster
501
2
555 timer question & "Bounceless" Garage door opener.

When opening a garage door from a distance, it is sometimes necessary to push the button multiple times when beyond the range of the transmitter. One can inadvertnently push the button multiple times and cancel the door going up. To open the door, one must push the button three more times to go down, cancel, and go up.

I resolved to solve this problem. I built a "bounceless" switch with a 555 timer and a relay.

There are 3 leads going between the motor and radio receiver. 24 VAC, Common, and "relay". The radio receiver grounds the "relay" lead to signal the motor to close the door. All I needed to do was interrupt the "relay" leg. For my bounceless switch, the "relay out" of the radio receiver grounds the input of a 555 timer. The output of the 555 timer closes a contractor connected to "relay in" on the opener motor. I chose a resistor and capacitor that make the 555 hold the output down for about 4 seconds.

Now, if I inadvertently hit the button multiple times, the motor does not receive multiple open signals because the 555 is still "holding down" the button.

Here are the voltage requirements of my components.

Components
555 Chip - 4.5 to 15 VDC.
Relay - 9 VDC


Here are my available voltage sources
24 VDC in radio receiver
8 VDC in radio receiver.
17 VDC repurposed transformer.

Initially, I was hoping the 8VDC would be enough to close the relay, but it was not sufficient. Currently, I have the 17 VDC source powering both the chip and relay.


Ok. Finally my question.


Am I OK to have both the chip and relay powered by the 17 VDC source? The relay is on for only 4 seconds, so I'm not that worried about that burning up. The chip has a large input impedance, so it should be comfortable with 17 VDC.

Is the 555 forgiving enough that I could even use the 24 VDC from the radio receiver? This would be a much more elegant solution.
 

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  • #2
There are a lot of variants of the 555. WHich are you using? If it is CMOS, the 17 VDC source is a no-no. If it is the LM555 from TI (probably the most popular) the max VCC rating is 18 VDC so you are pushing your luck at 17 VDC and 24 VDC will kill it. You could try powering a regulator to drive the 555's VCC or just use a voltage divider if you want a quick and dirty solution (assuming you're not using a battery)
 
  • #3
The 555 should run on a lower voltage and drive a "open drain" FET that provides a path to ground for the higher relay voltage (through the relay coil). Don't drive the relay like that from the 555.

Also, the relay needs a protection diode across it. When the switch opens, the relay coil produces a voltage spike (from the collapsing inductor field) that typically turns circuits into "switch once only" devices.

Do a google IMAGE search for "555 drives a relay" and look at the IMAGES for one you like.
 
Last edited:
  • #4
Suppose the door is going down instead of up and you want to stop the door immediately. What will happen?
 
  • #5
flatmaster said:
When opening a garage door from a distance, it is sometimes necessary to push the button multiple times when beyond the range of the transmitter. One can inadvertnently push the button multiple times and cancel the door going up. To open the door, one must push the button three more times to go down, cancel, and go up.

I resolved to solve this problem. I built a "bounceless" switch with a 555 timer and a relay.

There are 3 leads going between the motor and radio receiver. 24 VAC, Common, and "relay". The radio receiver grounds the "relay" lead to signal the motor to close the door. All I needed to do was interrupt the "relay" leg. For my bounceless switch, the "relay out" of the radio receiver grounds the input of a 555 timer. The output of the 555 timer closes a contractor connected to "relay in" on the opener motor. I chose a resistor and capacitor that make the 555 hold the output down for about 4 seconds.

Now, if I inadvertently hit the button multiple times, the motor does not receive multiple open signals because the 555 is still "holding down" the button.

Here are the voltage requirements of my components.

Components
555 Chip - 4.5 to 15 VDC.
Relay - 9 VDC


Here are my available voltage sources
24 VDC in radio receiver
8 VDC in radio receiver.
17 VDC repurposed transformer.

Initially, I was hoping the 8VDC would be enough to close the relay, but it was not sufficient. Currently, I have the 17 VDC source powering both the chip and relay.


Ok. Finally my question.


Am I OK to have both the chip and relay powered by the 17 VDC source? The relay is on for only 4 seconds, so I'm not that worried about that burning up. The chip has a large input impedance, so it should be comfortable with 17 VDC.

Is the 555 forgiving enough that I could even use the 24 VDC from the radio receiver? This would be a much more elegant solution.
Bro, I think it is perfect with 17 VDC but only if you want to upgrade then try 24 VDC. By the way my Automatic garage door opener is a very old unit. So, I want to ask does your switch would work with my opener?
 
  • #6
meBigGuy said:
The 555 should run on a lower voltage and drive a "open drain" FET that provides a path to ground for the higher relay voltage (through the relay coil). Don't drive the relay like that from the 555.

Also, the relay needs a protection diode across it. When the switch opens, the relay coil produces a voltage spike (from the collapsing inductor field) that typically turns circuits into "switch once only" devices.

Do a google IMAGE search for "555 drives a relay" and look at the IMAGES for one you like.

Ok. Regulating voltage to 12 VDC. Installed diode in parallel with relay coil side to handle collapsing inductor field.

The 555 output is rated at 200 mA and I measured the relay drawing 20 mA at 12 VDC. Do I really need to make the 555 drive a transistor instead of driving the relay directly? Is there some other reason not to drive the relay with the 555?
 
  • #7
skeptic2 said:
Suppose the door is going down instead of up and you want to stop the door immediately. What will happen?

Door will bounce back when hitting an obstacle. Otherwise, you need to wait the 3 seconds for the 555 to reset. This is enough time for door to go through about 1/3 of its total travel.
 
  • #8
flatmaster said:
Ok. Regulating voltage to 12 VDC. Installed diode in parallel with relay coil side to handle collapsing inductor field.

The 555 output is rated at 200 mA and I measured the relay drawing 20 mA at 12 VDC. Do I really need to make the 555 drive a transistor instead of driving the relay directly? Is there some other reason not to drive the relay with the 555?

Not really. I just don't like driving things from 555's directly. But the main reason was because of the supply voltage.

At what output voltage is the 555 rated at 200ma, and at what VDD voltage?
 
  • #9
flatmaster said:
Door will bounce back when hitting an obstacle. Otherwise, you need to wait the 3 seconds for the 555 to reset. This is enough time for door to go through about 1/3 of its total travel.

Which brand of garage door opener are you referring to? A garage door opener uses the breaking of the light beam as the first fault to cause the door to reverse. The door will also reverse if the door hits an object on the way down but the force it exerts on the object before stopping can be as high as 450 lbs. Garage doors have killed children.

For this reason you may want to reverse the door before it strikes an object and your circuit may prevent you from doing that. By the way, I used to be Sr. Electronic Product Engineer for the world's largest garage door opener manufacturer.
 
  • #10
It's an older model, so it doesn't have the light beam. Manufacture is Allister. Radio receiver is delta 3.

Not sure what the force required for bounce back is. I think I'll put some aluminum cans and see if it crushed them.

The delay I built is only on the radio receiver. Hard wired switches go directly to the opener and allow for a quick stop of the door.

I figure you'll only be closing the door with the remote when leaving. The door would typically opened just before you leave and closed as soon as you exit.

I'm glad to have a garage door engineer reading my post!

What about doors in commercial applications that close on their own after a period of time? Do they have the bounce back threshold set lower?
 

Related to 555 timer question & Bounceless Garage door opener.

1. How does a 555 timer work in a bounceless garage door opener?

A 555 timer is an integrated circuit that can be used as a timer, oscillator, or flip-flop. In a bounceless garage door opener, the 555 timer is used to generate a stable output signal that ensures the garage door opens and closes smoothly without any bouncing or jerking movements.

2. What is the advantage of using a 555 timer in a bounceless garage door opener?

The main advantage of using a 555 timer in a bounceless garage door opener is that it provides a reliable and consistent output signal. This helps to prevent any unwanted movements in the garage door and ensures safe and smooth operation.

3. Can a 555 timer be used in all types of garage door openers?

Yes, a 555 timer can be used in most types of garage door openers, including chain drive, belt drive, and screw drive openers. It is a versatile and widely used component in electronic circuits, making it suitable for various applications.

4. How is the 555 timer set up in a bounceless garage door opener?

The setup of a 555 timer in a bounceless garage door opener may vary depending on the specific design and circuitry. However, in general, the 555 timer is connected to a power source, a trigger input, and an output to control the garage door motor. Additional components, such as capacitors and resistors, may be used to adjust the timing and output signal.

5. Are there any potential drawbacks of using a 555 timer in a bounceless garage door opener?

While the 555 timer is a reliable and widely used component, it may have some limitations in certain applications. For example, it may not be suitable for high-speed operations or in extreme temperature environments. It is important to carefully select and test the components in a bounceless garage door opener for optimal performance and safety.

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