Controlling LED sequence with switches
Posted 07 March 2013 - 01:38 PM
My problem seems simple compared to the other posts i have seen in this forum so i hope someone can help. I have to install 4 LED's into the a sectioned cylinder of an engine to be put on display, i have 2 switches which are triggered on or off each time the piston hits them, hence giving me 4 inputs, i need a specific coloured LED to come on with each input, something like so:
Switch 1 On, Switch 2 off: White LED (Intake stroke)
Switch 1 On, Switch 2 on: Blue LED (Compression Stroke)
Switch 1 off, Switch 2 on: Red LED (Expansion stroke)
Switch 1 Off, Switch 2 off: Green LED (Exhaust stroke)
This happens in all 4 cylinders but if i can get it working on just 1, i can connect the rest of the cylinders in series or parallel accordingly. I have made a basic logic circuit in labview for this:
The 4 LED's also require 3.9 V at 350 mA to work at their optimum, and I'm having a hard time trying to figure out how/what functions to use as well as what channels to use. I did go through some the examples given (which i downloaded from this site) and it seems i can adjust voltage on the DAC channels to 3.9 Volts but i dont know how to get it to on 350 mA or to turn off when the switch is pressed etc
I'd really really be grateful if you can help.
PS. I have a Labjack U3-HV
Posted 07 March 2013 - 01:50 PM
In LabVIEW check out the easy function example "U3 eDI Example.vi".
Normally you power small LEDs with a voltage source and put some resistance in series to limit the current:
Your LEDs, however, need a lot of current. A current source would be better, but you should be able to use a voltage source as long as you use a current limiting resistor than can handle the power it is dissipating.
The control methods from the LED app note will not work for a 390mA LED. Rather you need some sort of switch that can handle the 390mA (SSR or transistor for example), and then use a digital I/O from the U3 to control that switch. If you want to buy something check out the PS12DC:
Posted 07 March 2013 - 01:55 PM
Posted 13 March 2013 - 03:10 PM
And I suppose i can use just 1 battery to power all the 4 outputs, as no two LEDs light on simultaneously, right?
something like so with a 3.9 volt battery:
Posted 13 March 2013 - 03:47 PM
As a side note, 350mA LEDs must be very very bright? 350mA seems well above average...
Posted 13 March 2013 - 04:59 PM
I'll see if I can find a 12V 350A ac/dc adapter and use that instead of a battery, and then connect 4 colours in series instead of parallel, 3V across each should suffice.
Thanks a lot for all the help, you guys are great :D
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