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piggles
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Joined: 15/10/2017
Location: New Zealand
Posts: 3

Posted: 12:44pm 01 Nov 2017

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Hi guys

I have a garage door opener remote with 3 spare buttons on it. From reading the instruction manual for the door (Conqueror model FBC200) I know the frequency of the opener is 433.92mhz

The project I am embarking on is a parking assistant using Arduino and a sonar module. I have no power point nearby so I am thinking of using an ATtiny85 so I can use batteries to power it. The idea will be to push a button on the key fob remote to wake up the ATtiny and give a visual indication of how far I can safely go into the garage.

Any ideas on how I can program one of the spare remote buttons?

Alastair
Senior Member

Joined: 03/04/2017
Location: Australia
Posts: 161

Posted: 01:18pm 01 Nov 2017

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Piggles (!!)
I would think that the battery drain associated with listening for a fob signal would be little different than simply pulsing the u/s occasionally to see if there is a target.

In another thread someone purchased a small solar light from Bunnings and stripped out the solar panel and battery to power a small device. Unless your garage is totally dark this may be worth looking at.

Cheers, Alastair

piggles
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Joined: 15/10/2017
Location: New Zealand
Posts: 3

Posted: 01:46pm 01 Nov 2017

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Thanks Alastair -

I think you're probably right about current drain, so I might have to rethink things. Only problem with pulsing to see if there's a target is it would need to be pulsed just about all the time because it could be needed at any time of day or night.

I thought about an LDR and flashing the car lights at it but that's not an exact science because of differences in ambient light. I may have to perhaps use a laser beam instead. I've just finished a snail mail notifier using a laser, and I had to put 3 layers of smokey plastic (from the plastic bag the laser came in) over the detector so it would just read the laser and not the daylight coming in through the slot.

I'll certainly think about the idea of solar too.

John

erbp
Senior Member

Joined: 03/05/2016
Location: Australia
Posts: 195

Posted: 01:49pm 01 Nov 2017

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Another possible approach might be to install a switch that is operated by the garage door opening which would then power up the Arduino and power it down again when the door closes. A magnetically operated reed switch or a lever operated microswitch might be suitable if you can find a way to mount it so that it would be operated when the garage door reaches the fully open position.

There was an Ultrasonic Parking Assistant based on a Micromite that was described in the Silicon Chip magazine March 2016 issue. I have one of these in my garage and can vouch for its usefulness in a tight parking situation. I have mains power available so it is powered on continually via a USB charger plugpak, although I did add a modification to allow the LED backlight on the LCD screen to be turned off when there is no movement being detected (which is 99.9% of the time).

Phil.

Alastair
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Joined: 03/04/2017
Location: Australia
Posts: 161

Posted: 02:02pm 01 Nov 2017

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John,
If the u/s transducer is pointing at the garage door then pulsing once every minute would probably be enough and use very little power. I do not know the ATtiny but assume that you can just single shot the tx. I have used an u/s tx with an E28 MM to measure water levels and when pulsed infrequently they use very little power.

I would not bother with LDRs, lasers etc. You already have the u/s Tx for the main game, so use it. Anything else is just going to increase power consumption.

Cheers, Alastair

piggles
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Joined: 15/10/2017
Location: New Zealand
Posts: 3

Posted: 02:37pm 01 Nov 2017

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@erbp - Great suggestion. I've just looked at the door in the open position and the handle for manual opening comes to rest within millimetres of the control unit for the opener, so I should be able to mount a small magnetic switch on the end of the handle. That would allow me to turn on the ATtiny only when the door is open, and for about 2 minutes only, in case the door is just opened without the car being used.

@Alastair - thanks for your input too. FYI - the ATTiny is a low power mcu from the Arduino family with 6 i/o ports on an 8 pin DIP. It's a breeze to work with and when in sleep mode draws just 1uA!

John

cs41
Newbie

Joined: 08/08/2016
Location: Australia
Posts: 28

Posted: 06:07am 02 Nov 2017

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hi all again,

I have successfully used an LDR setup for a gate opener for many years now without any problems.

To avoid ambient light variations causing false triggers it is best to only respond to sudden changes in light levels such a headlight flashes. Slowly changing sunlight and shadow will not affect it.

Using an LDR capacitively coupled to the base of a transistor does the trick.

As I am currently away in Hawaii (for work I might add !) don't have exact circuit values with me. Will try and look at it when I return next week if anyone wants more details.

Has been working reliably for a long time now on our front gate.

Actually is an interesting setup using a relatively cheap ( < $100) satellite TV linear actuator to drive the gate. I avoided too much electronics because of possibility of nearby lightning strikes damaging sensitive components so used hard wired relays as logic with just one transistor in the light sensor circuit.

If anyone needs more details please let me know.

regards

cs41

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