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Review: Paradise Arcade Shop 2 1/4'' Trackball
DaOld Man:
Actually those resistors are in line with the diodes. I should have drawn the leds with circles around them. The leds are on the right side of the inverters, 3 diodes on the left side. Best I can tell, pressing the mouse buttons puts a high on the diodes, which puts a high on the inverter inputs (buttons are not in this drawing, but connect to the arrows running off left of drawing).
Looks like the final inverter outputs connect directly to the leds.
I cant find any resistors at all in line with the leds.
BobA:
Sorry got mixed up between the blocking diodes with resistors and LEDs. The gates must have some internal characteristics that control the current. One of the uses is apparently sinking high current loads which in their example they cite being able to sink 2 TTL loads. A regular TTL gate can sink 10 standard loads or 16 ma so some sort of internal circuitry must be doing current limiting to sink the LEDs.
Just a thought that it maybe why they use 2 leds for each color. It could be part of the current limiting of the gate since they are bright and they probably could have got away with just 1 of each color. Maybe they need 2 so that one LED will not overcurrent and burn. Using 2 splits the current evenly if they are using the current limiting of the gate.
DaOld Man:
Thanks Bob, I did some research on that chip it is indeed current limiting as you said, so that explains a lot.
So if one of the leds burns out, the other will most likely follow. Seems to me that a much better solution would be to use current limiting resistors on each diode, but that might cost them a few cents more.
dawen:
--- Quote from: DaOld Man on January 02, 2012, 07:40:43 pm ---And here is the circuit after my proposed hack to the printer port.
pin 2 will light the ball red when turned on.
Pin 3 will light the ball green.
Both on maybe purple??? I doubt it, but I shall see.
--- End quote ---
I know this is an old thread but is there an easier way of explaining this for us idiots that dont understand the drawings?
What i would like to know is if there is an easy way without soldering to change so the red leds light up as standard instead of the green.
DaOld Man:
You can swap the 2 pairs of leds around to get the different colors, but it will require some soldering.
I would be glad to do that for you, if you want to mail just the board to me. PM me if you want to do that.
You can also cut out the 4 leds and use another led to light it from the hole in the center, underneath the ball.
This is what I have decided to do with my trackball.
I cut the 4 leds out, and am lighting it from underneath with a tri color LED assembly made to go on buttons. The led assembly is available from groovy game gear.
I dont have any pics yet, but am planning on using it on my "A Little Rage" build over in Project Announcements.
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