View Full Version : Remote on-off control modification
Needed to turn off another device at the remote site to save battery power at night when said device is not being used.
Tap into the postive side of a signal led and use the Advance tab "Signal LED Thresholds" option to turn the led off and on hooked to a simple NPN transistor switch with relay.
http://i188.photobucket.com/albums/z286/runnout/NS5.jpg
Circuit below:
http://i188.photobucket.com/albums/z286/runnout/switch.jpg
UBNT-Mike.Ford
10-29-2008, 01:39 PM
Pretty cool!
Mike
How do you turn it back on ????
[edited and added]
I'd use a small CMOS quad NOR gate package and put a time delay.
skyhook
10-29-2008, 04:02 PM
How do you turn it back on ????
Advance tab "Signal LED Thresholds": changing thresholds value...
And how in the world can you do that????
Change the LED threshold value which (controls the switch) to zero. The relay will go off.
If you want to turn on change the threshold value to like 90 to keep on.
You must be connected to have a stable signal on the LED you are using.
Try it and you'll see the LED turn off and on. The Positive side of the LED will read about 3.0 volts when on and zero when off.
Maybe I'm missing something here...how can you control a NS that is turned off in the first place. If its turned off, you'll not going to be able to access it to change the threshold level
[edited]
Oppps...I missed the part about turning off ANOTHER DEVICE. OK, now it makes sense what you're doing.
Wifi442
12-07-2008, 11:11 PM
This is a great idea! Could have many uses.
Any chance you could list the type of transistor and value of the resistor?
Would transistor 2N3904 (http://www.radioshack.com/product/index.jsp?productId=2062609) work?
Typically for a small relay, the basr resistor is 10Kohms. I would add a pull down resistor to the base pin to prevent it going negative when the transistors turns on and off.
A good relay might be
http://www.radioshack.com/product/index.jsp?productId=2062482
guidonet
12-08-2008, 05:02 AM
Cool... if you got a few units to turn on and off.
kijoma
12-08-2008, 01:33 PM
hi,
save a resistor , use an enhancement mode FET, plenty of logic level FET's out there. being voltage driven they wont suck any current from the LED feed etc..
www.siliconix.com
www.irf.com etc..
Also another option if you want to isolate the NS from the switched circuit (i.e. put the relay in the other device or near it then use a logic level opto isolator. connect that to the LED feed and ground and then you will have an isolated transistor output with no power connection to the NS.
I was thinking like the IRF1010 that I use all the time, but not sure if that's a Radio Shack item. Though you'd still need a pull-down resistor.
http://www.irf.com/product-info/datasheets/data/irf1010e.pdf
But I think some of those are discontinued.
kijoma
12-08-2008, 02:32 PM
pull down resistor? , on the gate?, depends if the driver for the LED is totem pole or open source/drain :)
if its totem pole then no need.
