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4 pin 2 colour LEDs exist in SMD but are wide angle.
What Colours, brightness and dispersion angle do you need? and Would like to have? (keeping a mind to availability).
The CR123A's sound like a plan. With the increase in high power LED torches they are much more abundant than they used to be which is good. However until I know the full amount, I will hold of speculating on the battery.I think the best battery is one with high power density, stable voltage and closest to the LED voltages and low cost.
That would be the CR123A battery Lithium, 3.0V using a MOSFET switch (RdsON< 1Ohm) would work well for B,G,W and 2V for R,Y,O options with a 1V drop resistor. A full wave bridge IC in SMT would be good for bi-directional colour drivers for low current or equivalent.
AS Brian indicated ( no pun intended) you can get very high Candle power at 20mA so you often dont need more than 5mA for indicators.
For more constant current thruout the entire SoC range a 3.6V LiPo is perfect or string many 16850 cells in series to have the discharge time you specify that you need and run strings in series.
Sorry to be ambiguous, but I don't really want to mention the game in question directly. It's not mine and it's only just been released.I am still confused how these LEDs are supposed to look.
What game is it and what is the function and orientation of each LED in time or position.
I have RGB through-hole LEDs with a common cathode (but I find they are ugly - like cheap looking fairyland Christmas lights, and without sufficient current-limiting are possibly retina damaging devices!), four pins, if you use a PIC I guess you can set via the code the required voltage to turn each colour on, but I found they respond to "any old" voltage which would make using them a lot easier.
PP3 are perhaps a poor choice, unless the game will only last a few minutes or the power consumption is low. Here's an example datasheet:
https://data.energizer.com/PDFs/522.pdf
"Can 9v be amplified/stabilised so that even when the cell drops there is still a constant steady supply?"
- I read a datasheet the other day, but can't find it now, for what I think was more or less called a "buck/boost converter" or "buck/boost switching regulator" - it regulates the supply voltage down to the required voltage, then when the battery (voltage) has dropped to lower that the required voltage boosts the supply up, it looked a really handy device, sorry I can't find the datasheet or name...
You can use buck/boost to hold the voltage steady but it would be far more complicated than a bigger battery and the life may not be extended anyway. The extra current drawn in buck mode would place extra drain on the battery and in boost mode it converts additional current into the added voltage so the drain becomes even greater. It's good technology in some circumstances but as a way of extending the life of a feeble and non-renewable power source it isn't really suitable.
I would urge caution about recommending any particular battery type until the total load can be confirmed. The switch end would probably draw < 1mA and my best guess at the LED end is it could be as much as 24 * 5mA = 120mA but what isn't known is how many of these LED game peices will be on the board at a time. The total could be considerbly more than a small battery could manage.
Brian.
What game is this for?
Sorry to be ambiguous, but I don't really want to mention the game in question directly. It's not mine and it's only just been released.
Are you saying that unplugging the piece and putting it in a different socket (board location) may change the required combination of LEDS?the 6 switches that affect the lights on the piece change relative to the pieces position.
Which, after my first mistake of not including a series resistor at all was how I was assuming they would be wired anyway. Good to know that is acceptable.I'm not suggesting the LEDs should be wired across each other directly, that wouldn't work for the reasons already given. There is nothing wrong with wiring a resistor in series with each LED then wiring that series combination in parallel.
Thanks - I was getting mixed up between the 3 pin and 2 pin LED's120mA is way too much to consider, you can drop the transistors if you keep the total current for the 4 LEDs below about 20mA. Let one PIC pin source the current and another pin sink it. If you use 12 pins, 6 as source, and 6 as sink, you can reverse both their polarities to change the colour and then use 2 pin bicolour LEDS. Cheaper LEDs and no transistors needed! A 16F628 has 16 input/output pins, you are using 2 for the serial link so if you use the remaining 12 for LEDs you still have 2 spares.
Brian.
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