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Simple transmitter/receiver

Posted on 2004-08-11
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Last Modified: 2013-12-09
I need a simple rf circuit to detect that some one has pressed a button thats it. I dont care who pressed the button just that a button was pressed. I want some thing very simple but it has to be reliable no false triggers from stray rf signals?

What im after is a simple transmitter that a person can hold then press a button which is then picked up by the receiver? there can be multiple people holding transmitters.
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Question by:julianpointer
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13 Comments
 
LVL 2

Expert Comment

by:marius_petrescu
ID: 11780447
Get trransmitters (including the button) and receivers from a car alarm.

They use digital codes (no false triggers) and you have 2 tx and 1 rx to start and can get aditional transmitters....
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LVL 69

Expert Comment

by:Callandor
ID: 11783496
Garage door openers are another source - you can open one up to see how it's done.
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LVL 3

Author Comment

by:julianpointer
ID: 11788112
I need  the tx to be cheap... probably more than 500 tx to a rx, i was thinking more of a tuned frequency?
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LVL 2

Expert Comment

by:marius_petrescu
ID: 11788730
the tx on a simple burglar/theft alarm or car alarm is cheap, and has a reasonable design. You just have to use a cutter or drill to set the 8 bit code... Any quantyties are available. The one with only 1 push button.
I think the whole 2 tx + 1 rx is abt. 60$, 1 tx in the range of up to 5$, cann not tell you exactly. Maybe you could even get a quantity discount.
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LVL 10

Expert Comment

by:Dynamic1
ID: 11789377
Julian even fixxxed freq will have false alarms without a code.
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LVL 55

Expert Comment

by:Jaime Olivares
ID: 11790063
I know there are wireless door chimes that cost about $10.
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LVL 27

Expert Comment

by:d-glitch
ID: 11794074
I have bought KEELOC keychain XMTR's and small RCVR's from Digikey.  Search for RF transmitters.  between $20 and $50

                                             http://www.digikey.com/

The manufacturer also has a website.

                                             http://www.rfsolutions.co.uk/products/remote_control_systems/keeloq_high_security.htm

You can have multiple XMTR's.
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LVL 27

Expert Comment

by:d-glitch
ID: 11794187
Digikey also has products from LINX techmnologies.

                        http://www.linxtechnologies.com/

I haven't used them.  But the quantity price goes down to approx $5.
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LVL 22

Expert Comment

by:grg99
ID: 11795419
What kind of distance do you need?

What level of reliability. both for extra hits or misses?

What level of security against other unauthorized people setting off your receiver?

Without that info we cant be of much help.

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LVL 3

Author Comment

by:julianpointer
ID: 11797167
Distance < 25m
Realibility: No false hits from broadcast transmissions
Security: None

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LVL 22

Accepted Solution

by:
grg99 earned 1000 total points
ID: 11798199
Okay, then your typical auto-alarm rx/tx should do the trick.  As others have noted these are available for not too many $.

 
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Expert Comment

by:rsinisa
ID: 11990970
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