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'[EE] Garage door open detector'
2011\10\11@231704 by V G

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Hi all,

I want to make a simple, cheap, quick, reliable (no one dare say you can
only pick only x) garage door open detector that will light up an LED in the
house/beep a speaker if the garage door is open. I know all it takes is a
mechanical switch, but I'd rather not use any moving parts. I'm thinking a
very bright infrared LED and IR transistor with a piece of foil mounted on
the inside of the garage door. If the door is closed, a series of LED pulses
will hit the aluminum foil reflector and bounce back to the IR transistor
and signal the device that the door is closed. Will this work? I've never
done any IR work, so I don't really know what power LED is required, what
the distances are, etc.

As for the micro controller unit, I can make it wireless and signal the
indoor unit via something like this
http://www.sparkfun.com/products/10534but I'd have to impliment
encryption on the micro controller itself. It
would also interfere with other units in the same band, which is very very
undesirable. How hard is it to implement simple encryption?

Xbee is cool, but it will add $40 at least to the cost of the project.

Any other ideas

2011\10\11@235528 by Bob Blick

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This is what I use for the sensor:

http://www.amazon.com/SECO-LARM-SM-216Q-Wide-Magnetic-Contact/dp/B002ZOQ0RQ

Bob

On Tuesday, October 11, 2011 11:16 PM, "V G"  wrote:
{Quote hidden}

-- http://www.fastmail.fm - Does exactly what it says on the tin

2011\10\12@004910 by IVP

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I have something along those lines using a rolling ball tilt switch. Been
outside for years, dirt cheap, works fine

RBS040200

http://nz.mouser.com/ProductDetail/OncQue/RBS040200/?qs=sGAEpiMZZMuRFIlaTiDGnyO9S6YqVdv1g3%2Ft0AF3r3Y%3D

Joe

2011\10\12@005642 by Brent Brown

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{Quote hidden}

On the simple side of things, but... I set one up for my parents garage door (tilt door) many years ago. Used a long lever microswitch that the door operates when fully closed, normallly open and normally closed contacts arranged so that a green LED lights for fully closed, red LED for door open any amount. Stole 12V DC power from the door opener somehow, 3 wires in underground cable to remote LED's in house. The microswitch does need pushing around and readjusting every now and then for I don't know what reason, but basically still working fine after maybe 25 years.

Get calculator... that means the green LED has probably done 200,000hrs~! (Assuming door closed 90% of the time). Assuming 15mA current that's 3000Ahrs, LED has resistor of 12VDC supply, say 90% PSU efficiency that's approx 140Ahrs @ 230VAC, assume power factor unity then that's 32kWhrs,  @ say $0.20 average per kWhr unit = $6.40 electricity for 25 years of operation.

-- Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  spam_OUTbrent.brownTakeThisOuTspamclear.net.nz

2011\10\12@010004 by IVP

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> will hit the aluminum foil reflector and bounce back to the IR transistor
> and signal the device that the door is closed. Will this work? I've never
> done any IR work, so I don't really know what power LED is required,
> what the distances are, etc

It will work, it's the basis of some shop door beepers. I've got a friend's
here right now. It's not very well. The reflector is faceted, presumably to
bounce signal back to whence it came at whatever angle it whenced. Not
as good as the one they left on the moon probably. It's a similar effect to
the retroreflective coating on road signs

Overall LED power doesn't need to be much. Just ping it every second
with a quick burst. At 5V the current limiting resistor can be quite small,
10 ohms or less, if the pulses are kept fairly short, eg 1ms. Most IR LEDs
will take several amps for short periods. If you notice the LED getting
warm you're probably close to too much

Jo

2011\10\12@034844 by Electron

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At 05.16 2011.10.12, you wrote:
{Quote hidden}

I was faced with the same problem too: after investigating and trying many
solutions, I went with a magnetic solution. Attaching a magnet on the garage
door was easy (as it's ferrous).

In my case it calls me on the phone..

Regards,
Mario

2011\10\12@043226 by alan.b.pearce

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> It will work, it's the basis of some shop door beepers. I've got a friend's
> here right now. It's not very well. The reflector is faceted, presumably to
> bounce signal back to whence it came at whatever angle it whenced. Not
> as good as the one they left on the moon probably. It's a similar effect to
> the retroreflective coating on road signs

As in bicycle reflector.


-- Scanned by iCritical.

2011\10\12@043928 by Geo

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V G wrote:

> I want to make a simple, cheap, quick, reliable (no one dare say you can
> only pick only x) garage door open detector that will light up an LED in the
> house/beep a speaker if the garage door is open.
Does it matter if the door is closed but not locked?

George Smith

2011\10\12@050942 by IVP

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> As in bicycle reflector

That's true, you can get clear ones for the fron

2011\10\12@090330 by Carey Fisher

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On Tue, Oct 11, 2011 at 11:16 PM, V G <.....x.solarwind.xKILLspamspam@spam@gmail.com> wrote:

> Hi all,
>
> I want to make a simple, cheap, quick, reliable (no one dare say you can
> only pick only x) garage door open detector that will light up an LED in
> the
> house/beep a speaker if the garage door is open.
>
..........

> Any other ideas?
>
> I've used this for several years with no problems. Trivial install.  Change
batt every 5 years.  Place indicator anywhere in the house.

http://www.chamberlain.com/doityourself/pages/productmodeldetail.aspx?modelId=1513

and it's only USD45.00

Carey Fishe

2011\10\12@103017 by Herbert Graf

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On Tue, 2011-10-11 at 23:16 -0400, V G wrote:
> Hi all,
>
> I want to make a simple, cheap, quick, reliable (no one dare say you can
> only pick only x) garage door open detector that will light up an LED in the
> house/beep a speaker if the garage door is open. I know all it takes is a
> mechanical switch, but I'd rather not use any moving parts. I'm thinking a
> very bright infrared LED and IR transistor with a piece of foil mounted on
> the inside of the garage door. If the door is closed, a series of LED pulses
> will hit the aluminum foil reflector and bounce back to the IR transistor
> and signal the device that the door is closed. Will this work? I've never
> done any IR work, so I don't really know what power LED is required, what
> the distances are, etc.

Unless you interested in learning about that kind of stuff, don't
bother.

Just get the type of sensor alarm systems use. One end is just a magnet,
the other is a reed type switch. VERY reliable, VERY cheap. You can find
them pretty much everywhere. Easy to mount to. That's what I use.

TTYL

2011\10\12@104455 by Kerry Wentworth

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Herbert Graf wrote:
{Quote hidden}

Kerry

2011\10\12@111030 by Joe Wronski

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On 10/11/2011 11:16 PM, V G wrote:
{Quote hidden}

I'm curious, why is encryption an issue?  Who, within 400 ft of your garage, and with the receiver to read the signals, would care about the state of the door?
As for interference, low data volume and low update frequency stuff like this spends very little time on the air.    You could send one or more 10 mS burst at some fairly large interval (minutes) and be reasonably up to date with the door.   That shouldn't be a problem unless it interferes with something that is data critical.

Joe W

2011\10\12@120325 by doug metzler

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I've played around with those sparkfun transmitter/receivers.  the
biggest problem is that what you send isn't always what you get, so
you'll need to implement some sort of error correction or multiple
message protocol.

I eventually went to modules that have error correction built in.
They're more expensive.

DougM

On Wed, Oct 12, 2011 at 8:11 AM, Joe Wronski <jwronskispamKILLspamstillwatereng.net> wrote:
{Quote hidden}

>

2011\10\12@130016 by YES NOPE9

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{Quote hidden}

If this is for fun ........ and a learning experience......
Use an Xbee pair of transceivers ( home and door ) .... send a serial stream to the garage door transceiver  ... at the door use the serial stream to drive an infrared LED.  Use an infrared receiver to produce the same serial stream back into the garage Xbee.  Then look for that stream at the home Xbee.

Xbee could replaced by bluetooth modules or TI low power RF  ( CC115L transmitter, CC113L receiver and CC110L transceiver ) or many other RF solutions..  I can say more if you are interested.
99guspuppet

2011\10\12@133306 by Joe Wronski

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We (Fitsense, now Fitlinxx) used RFM 300 and 900 Mhz transmitters and receivers and yes, they are susceptible to noise getting in, so we used a checksum scheme to check the packets.  If it was 2 way, the unit acting as master would re-request any corrupted messages.  One way beacons were sent once per second, and if some were lost, it was not a big deal.  This was speed and distance data sent from a footpod to a wristwatch.
They are using Nordic 2.4 gig modules now, and the burst mode makes it much less load on the processor, as the receiver does all the error and address checking, and data can be clocked in / out at any speed.
So, we had error detection, and error correction was not needed.
Joe W

On 10/12/2011 12:03 PM, doug metzler wrote:
{Quote hidden}

>> -

2011\10\12@160603 by V G

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On Wed, Oct 12, 2011 at 4:39 AM, Geo <EraseMEbuggiesmithspam_OUTspamTakeThisOuTgmail.com> wrote:

>  Does it matter if the door is closed but not locked?
>

In this case, closed is always locked

2011\10\12@160724 by V G

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On Wed, Oct 12, 2011 at 1:00 PM, YES NOPE9 <yesspamspam_OUTnope9.com> wrote:

>  If this is for fun ........ and a learning experience......
> Use an Xbee pair of transceivers ( home and door ) .... send a serial
> stream to the garage door transceiver  ... at the door use the serial stream
> to drive an infrared LED.  Use an infrared receiver to produce the same
> serial stream back into the garage Xbee.  Then look for that stream at the
> home Xbee.
>

That sounds like a good idea, since it seems there isn't a cheap way of
neatly getting out of this.


> Xbee could replaced by bluetooth modules or TI low power RF  ( CC115L
> transmitter, CC113L receiver and CC110L transceiver ) or many other RF
> solutions.  I can say more if you are interested.
>
>
Please post more

2011\10\12@161102 by V G

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On Wed, Oct 12, 2011 at 11:11 AM, Joe Wronski <@spam@jwronskiKILLspamspamstillwatereng.net>wrote:

> I'm curious, why is encryption an issue?  Who, within 400 ft of your
> garage, and with the receiver to read the signals, would care about the
> state of the door?
> As for interference, low data volume and low update frequency stuff like
> this spends very little time on the air.    You could send one or more
> 10 mS burst at some fairly large interval (minutes) and be reasonably up
> to date with the door.   That shouldn't be a problem unless it
> interferes with something that is data critical.
>

There are many things in life that one can get away with, with a very low
probability of consequences. But I am a man of principles.

Yes, I can get away with a $10 pair of unreliable radio modules without
encryption, which will block those frequencies/receive interference, but I
choose not to. I always leave room for expansion. Looks like I'll need to
stick with xbee modules and probably a wide temperature PIC 18

2011\10\12@175046 by Joe Wronski

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On 10/12/2011 4:10 PM, V G wrote:
> On Wed, Oct 12, 2011 at 11:11 AM, Joe Wronski<KILLspamjwronskiKILLspamspamstillwatereng.net>wrote:
>
>> I'm curious, why is encryption an issue?  Who, within 400 ft of your
>> garage, and with the receiver to read the signals, would care about the
>> state of the door?
>> As for interference, low data volume and low update frequency stuff like
>> this spends very little time on the air.    You could send one or more
>> 10 mS burst at some fairly large interval (minutes) and be reasonably up
>> to date with the door.   That shouldn't be a problem unless it
>> interferes with something that is data critical.
>>
> There are many things in life that one can get away with, with a very low
> probability of consequences. But I am a man of principles.
>
> Yes, I can get away with a $10 pair of unreliable radio modules without
> encryption, which will block those frequencies/receive interference, but I
> choose not to. I always leave room for expansion. Looks like I'll need to
> stick with xbee modules and probably a wide temperature PIC 18.
I don't know if that is a condemnation of the policies of the regulatory agencies we adhered to, or a proclamation of wanting a higher standard.
Joe

2011\10\12@183151 by V G

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On Wed, Oct 12, 2011 at 5:51 PM, Joe Wronski <RemoveMEjwronskiTakeThisOuTspamstillwatereng.net>wrote:

> I don't know if that is a condemnation of the policies of the regulatory
> agencies we adhered to, or a proclamation of wanting a higher standard.
>
>
I don't understand, please explain

2011\10\13@000514 by Joe Wronski

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On 10/12/2011 6:31 PM, V G wrote:
> On Wed, Oct 12, 2011 at 5:51 PM, Joe Wronski<spamBeGonejwronskispamBeGonespamstillwatereng.net>wrote:
>
>> I don't know if that is a condemnation of the policies of the regulatory
>> agencies we adhered to, or a proclamation of wanting a higher standard.
>>
>>
> I don't understand, please explain.
Excuse me, I was out of context.  I thought that you were replying to another post where I had described that we used 300 and 900 Mhz radios at a previous $JOB.   You spoke of the probability of consequences,  of principles, encryption. co-existence with other radios, and room for expansion.

We used RFM 300 and 900 Mhz radios very similar to the inexpensive unreliable modules you can  buy at Sparkfun.  Our RF protocol was designed to operate within the limits of FCC regulations.  This was accomplished by controlling the amount of time spent transmitting, along with controlling transmit power and suppressing harmonics.   It was a very simple, limited system, maybe a little more than would be needed for a door status indicator.   The consequences arising from someone using a 900 Mhz telephone while our system was trying to communicate were acceptable. The consequences from having an unreliable connection were dealt with at the application layer, with error detection, not correction.  Reliability was increased some by using bit stuffing to ensure that not too many consecutive 1's or 0's were transmitted in the OOK stream.  Encryption was a very simple x-or with a secret string, about all we had code space for.
If the purpose of this project is part of a learning experience, and a building block for a more sophisticated system, go with the more expensive modules.  But I think monitoring a door can be done with simpler components, co-existing with other radios, without compromising your principles.
Joe W

2011\10\13@002650 by V G

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On Thu, Oct 13, 2011 at 12:05 AM, Joe Wronski <TakeThisOuTjwronskiEraseMEspamspam_OUTstillwatereng.net>wrote:

> If the purpose of this project is part of a learning experience, and a
> building block for a more sophisticated system, go with the more
> expensive modules.


Well said, that may in fact be the case - a building block for a more
sophisticated system. I guess I'll use xbees.


> But I think monitoring a door can be done with
> simpler components, co-existing with other radios, without compromising
> your principles

2011\10\13@025228 by Christopher Head

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On Tue, 11 Oct 2011 23:16:49 -0400
V G <RemoveMEx.solarwind.xspamTakeThisOuTgmail.com> wrote:

> Xbee is cool, but it will add $40 at least to the cost of the project.
>
> Any other ideas?

Replace XBee with MRF24J40MA you can change $40 to $20 for a pair, with
virtually identical power output and receiver sensitivity specs.

I haven't tried them, but I have a board on order to try them as a
replacement for XBees very soon and I have gone through the datasheets.

Chris
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2011\10\13@090817 by Electron

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At 16.29 2011.10.12, you wrote:
{Quote hidden}

I second that. I made it myself, but I tried almost every possible sensor.
In the end magnet + reed (well, I used semiconductor hall effect sensor) is
the simplest, most reliable, cheapest and overwall best-working solution.

2011\10\13@155502 by V G

picon face
On Thu, Oct 13, 2011 at 9:07 AM, Electron <electron2k4EraseMEspam.....infinito.it> wrote:

> I second that. I made it myself, but I tried almost every possible sensor..
> In the end magnet + reed (well, I used semiconductor hall effect sensor) is
> the simplest, most reliable, cheapest and overwall best-working solution.
>

I'm going to try IR and see how it goes

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