Community Question

Ok so I need to make ir buy a light sensor that I can place ontop of my bot through a drilled hole on Omnibots head or neck area. I will have about 25-50 5mm forward facing ir LEDs and 25-50 inside omnibots eye sockets so it illuminates the most where omnibot is looking. They will all not even draw a amp because LEDs are so low power. Any ideas of how to switch on the LEDs? I would like for it to switch the IR on when it hits a certain level of darkness. I believe my IR LEDs run on 2.5v and draw .02A thanks
jstarne1
Commented March 2012
I would say its best to just use the ezb to trigger a low power relay. Like a reed relay from radioshack. This way.I can put a switch on the back of my bot so I can manually turn off the led lighting as it could be annoying at certain times. So is a comparitor circuit the way to do this? Agian I only want to use ezb as trigger I don't want to power any accessories with it.
robotmaker
Commented March 2012
it depends if you want to want to make a extra script for it and measure the phot cell analog output for darkness you have for it to come on using analog port,other is making a comparator circuit with parts from radio shack board and parts fairly cheap,then add a pot to adjust it and use a simple digital input script to trigger the digital output relay,reed switch is fairly good way to go,will need pnp transistor to turn it on from the digital port
mosfet is better and about the same price of reed relay plus transistor

keep in mind will need 25 resistors for 25 leds. for 20 ma at 5 volts supply 470 ohms
jstarne1
Commented March 2012
Larson scanner would be cool if it only came on when talking. Just like evolver . His was LEDs that would light in the center and go towards right and left edges.when.he spoke.
User-inserted image
robotmaker
Commented March 2012
you can use LM3915 circuit for mouth,when sound apply to input the leds move to be like he is talking
they sell board complete for it,i think website is canakits

here is is,you need 2 of them
led vu meter kit

or 10 led vu kit 1 of them can put in series
10 led vu mter kit
robotmaker
Commented March 2012
jstarne1 my friend i have over 100 reed relays i can sell you 2 for $1 plus postage of $1.69
have single pole single throw,and double pole single throw 5 volt coil at 50 ma
will need npn transistor for 2 reasons one is 25 ma max on digital output pin and coil takes 50 ma,same as one from radio shack
second reason is back emf they call it,when a relay coil turns off and on sends a magnet force that will ruin the output pin,and you dont want to ruin $130 board,plus across the ciol still need any diode cathode to v+ to protect the transistor ,since digital output uses one too
if you have problems hook it up let me know ,also from outpin on EZB to base of the transitor you need a base resistor mostly near 4.7k
hooking up transistor is easy emmiter to gnd collector to coil and anode of diode on other side of coil you connect 5 volt supply and cathode of diode

i just found this after i did this reply says the same thing i said
how to drive a relay from digital pin
Question
Avatarjstarne1
Asked on Saturday, February 25, 2012