altometer for model heli

[buttonswapper]

i want to build a circuit to switch on landing lights on the copter once she reaches about 4 foot from the ground. I can either use 9v or 4.5 volts the light preferably ultra bright LEDS thanks for your help

 

[jrz126]

I dont think an altimeter would do the job, because it's distance above sea level.

You might be able to do it with IR LED's and Sensors. I don't know how effective they are at a distance of 4 ft. Also, there really isn't a uniform object for it to reflect off of.

An ultrasonic transducer would do the job. It sends out ultrasonic soundwaves, and these waves echo off nearby objects and then you can measure the time between sending the wave and recieving the echo. then multiply that time by the speed of sound and you've got your distance but that would require a microcontroller, which gets fairly complicated if youve never used one before.


Hopefully I didn't confuse you even more.

 

[-=GST=- Nemisis (cs/cz)]

yes use ultra sonic waves and a chip to count the time it takes for the wave to bounce back and to put the LEDs on at different strengths or u will need to find/program a chip with how long it will take 4ft from the floor, u will need to do extensive research for that though.

 

[Oznog]

yes use ultra sonic waves and a chip to count the time it takes for the wave to bounce back and to put the LEDs on at different strengths or u will need to find/program a chip with how long it will take 4ft from the floor, u will need to do extensive research for that though.

Even smaller and easier to power might be an infrared LED sending out a pulsed signal. The range would certainly vary a lot depending on the reflectivity of the surface but it'll turn on or off at SOME point. Better yet would be to direct the tx and rx so that the reflection will only be visible if the ground is within a certain distance due to their angles. Lenses or even slits can do the job.