Software Support > Automated Projects
Circuits
DaOld Man:
Probably should, depends on the transistor's switching time.
wemr97dl:
I contacted Andy at ultimarc about Mosfets and he sent me a print of his trackball lighting kit, he used p-channel and i bought n channel, I just need something big enough to handle 39 RGB leds at 12 v, which would be 13 per channel, he used BSH201: P-channel vertical D-MOS logic level FET, what specs would i need to look at when picking one out??
DaOld Man:
--- Quote from: wemr97dl on May 23, 2016, 04:34:54 pm ---I contacted Andy at ultimarc about Mosfets and he sent me a print of his trackball lighting kit, he used p-channel and i bought n channel, I just need something big enough to handle 39 RGB leds at 12 v, which would be 13 per channel, he used BSH201: P-channel vertical D-MOS logic level FET, what specs would i need to look at when picking one out??
--- End quote ---
Sorry about the late reply man, I really need to start showing up here more often. (Life, leave me be!)
I would follow andys advice, he knows what he speaks of. (I forgot those cards put out a negative signal to turn on the load. )
Hows this project coming along?
wemr97dl:
Waiting on mosfets right now for the RGB Strips, but leaving for Vacation in a few days so I wont get back to it for a few weeks.
Here's a link to my project.
http://forum.arcadecontrols.com/index.php/topic,144775.0.html#lastPost
All that is left cabinet wise is Some button inserts for the start buttons and the Plexi for the monitor.
Got to get the RGBs running and start playing with LEDblinky and CPwiz for the second monitor, almost there
DaOld Man:
Using an opto isolator as an SCR.
SCR (Silicon Controlled Rectifier, a device which conducts a high current when a smaller current is applied to its gate. The current continues to flow until it is removed, regardless of gate current. Like a Latch)
I have a small project Im working on and I need an scr.
Radio shack doesnt have it and from the web I have to pay more for the shipping than I do for the part.
So I was thinking, surely I can substitute a part I already have in my junk box?
Well, the old reliable opto isolator came to mind.
On the test breadboard, I used a now obsolete TIL 119 but I dont see why any opto isolator wouldnt work.
What I needed to do was to turn on an led and keep it turned on until I pressed a reset button. I will do a build thread on what Im doing later.
Anyway, the way Im testing the TIL 199 is like this. (See attached diagram).
Pin 1, the anode of the internal led on the 199 connects to the emitter (pin 4) on that same chip through a 460 ohm resistor.
The cathode (pin 2) connects to ground.
The collector (pin 5) connects to + 5VDC.
The load Im will be using is an led with its matching resistor (not shown), which will connect to ground and pin 4. (the emitter)
The trigger that fires this baby also connects to pin 4 and a positive going current is needed.
How it works:
When pin 4 goes high through the trigger, current flows through the resistor and the chip's led, illuminating the led.
The led, when it lights, forward biases the chips transistor, which allows current to flow to pin 4, keeping the output high and the chip's led on after the trigger source is removed.
The output stays on until the pins 1 and 2 are shorted, or pin 2 is removed from ground. Either of these conditions will turn off the led and reset the circuit.
I found that the circuit powers up when power is applied, I dont know why, maybe a surge starts the transistor to conduct?
So I added the capacitor across pins 1 and 2 to short out the led for a very short time on power up. The short time is determined by how long the capacitor takes to charge.
A smaller value would probably work but thats what I had on hand.
Drawbacks of using this:
Output current is limited to what the Opto Isolator can handle.
Trigger source has to be able to supply output current level.
Trigger source cant go back to ground after going high (might could add a blocking diode if you really need to?)
Also this draws more current than an SCR would, due to the chips LED.
And it takes more parts to do what a small scr alone would do.
I know I can do the same with an OR gate, but I couldnt find one in my junk box.
So i will probably wind up ordering the scrs and paying the high shipping, but I thought some of you guys might find this interesting.
Anyway, hope you enjoy and feel free to add your comments.
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