Old RC toy made into a garage alarmPosted on January 4th, 2010 3 comments
My wife wants some sort of indicator to show when the garage door is open. The garage is visible through the back window, but sight lines make it difficult to determine. Also, when the shades are drawn, there is no visiblity. I considered X10 modules at first, but that just seemed like overkill when all I really wanted was a small led to illuminate.
Then, I remembered an old RC toy car my son had. The controller unit was simple, with just one button. Pushing the button made the car go forward. Releasing it made it go backwards while turning. On the receiver (car) side, the controller signal caused a voltage to toggle between -1.5 volts and +1.5 volts. With a little testing, I found a point that toggled between 0 and +3 Volts. This was just enough to provide drive an LED. A magnetic reed switch from Axman Surplus worked perfectly for the door sensor. This switch is in the off mode when the magnet and reed unit are near each other (door closed). When the door opens, the magnet will be pulled away and complete the circuit. The transmitter and switch are hooked up to a PIC16F684 chip. The reed switch is connected to pin 4, which is configured as a digital input. When the reed switch is open (door closed), the signal on pin 2 goes high. This turns on an NPN2222 transistor, which in turn causes the transmitter to send a signal. The receiving unit goes to +3 volts on the output when there is no signal, and drops to 0 volts when there is a signal. In other words, when the door is down, the LED indicator is off. This may seem overly complicated, but it has one advantage. If the garage-side (transmitting) unit fails, the light will come on. Although this may be a false positive for the door being up, it indicates that something is wrong on the transmitting side (power failure, loose wire?).
3 responses to to “Old RC toy made into a garage alarm”
Good day I am so delighted I found your website, I really found you by
accident, while I was researching on Askjeeve for something else, Nonetheless I am here now and would just like to say many thanks for a marvelous post and a all round enjoyable blog (I also love the theme/design), I don’t have time to browse it all at the minute but I have saved it and also added in your RSS feeds, so when I have time I will be back to read a great deal more, Please do keep up the excellent work.
I really like your blog.. very nice colors & theme.
Did you design this website yourself or did you hire someone to do it for you?
Plz answer back as I’m looking to construct my own blog
and would like to know where u got this from. appreciate
For celebrities who rely on the social network to promote their music and motion pictures, following
a handful of uncomplicated Facebook rules could do wonders for their brand
method. Did you know you can target certain audiences with posts
primarily based on location and language? Facebook also lets Pages users reposition photographs by clicking the edit pencil in the proper corner of the post.
For unique posts that you want to be front-and-center, click the star icon so
it spans across the major of your page. facebook likes buy australia (Ralph)
Leave a reply