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| GUN4IR - The Ultimate 4 Points Lightgun System |
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| Zebidee:
--- Quote from: pacooka on October 08, 2022, 08:06:47 am ---For the IR LED, I would like to use the black 940nm IR LED SIR5028B instead of the transparent ones because I heard they perform better. By looking at the calculator, I see that for VCC 1.2V I should use 47 Ohm (for transparent LEDs - 27 Ohm); can someone please advise if this is correct, or point me to the right black LEDs & resistors? --- End quote --- I know I'm coming in sideways and haven't read all the previous 25 pages of the thread, so I apologise if I misunderstand the context, but... It is generally better to run your LEDs in parallel rather than in series. That means each LED has its own resistor and 5v power (you daisy chain the 5v, much like we commonly do for grounds). If you have Vcc=5v, forward voltage over LED = 1.2v, want 10mA current, then 380R (for each LED) is the "right" resistor. This is the safe minimum, you can use higher value resistors safely (the LEDs will be less "bright"). As each resistor/LED pair is only passing 10mA current, you can use any old 1/4W or even 1/8W resistors, don't need to be high wattage rating. If wanted, you MAY add another resistor (one, in series) on the 5v supply, to all LEDs, to limit the current a bit more. Again, everything is going to be <30mA so 1/4W rated resistor is fine. You CAN wire all the LEDs in series behind a single resistor. However, in practice this often means the last LED is struggling to get enough current, especially as even the best 5v supply will have ripples. Makes the quality of your power supply more important. Also means a single fault anywhere prevents all from working, and makes it more difficult to troubleshoot. Love this project, been following for a while, really happy to see more great lightguns happening :D |
| RandyT:
--- Quote from: pacooka on October 08, 2022, 08:06:47 am ---For the IR LED, I would like to use the black 940nm IR LED SIR5028B instead of the transparent ones because I heard they perform better. By looking at the calculator, I see that for VCC 1.2V I should use 47 Ohm (for transparent LEDs - 27 Ohm); can someone please advise if this is correct, or point me to the right black LEDs & resistors? --- End quote --- The current to radiant intensity curve on this part looks to be very linear, and I assume that you want the maximum amount of brightness given that you seem to want to use this part for it's performance characteristics. This particular LED shows to have a continuous current rating of 20ma, so driving it at half that (your stated 10ma per part), while possibly increasing the longevity considerably, is likely to be giving up a good chunk of that performance. If it were me, and based on the data for the part, I would run them "hotter" at 16-18ma which should give them a higher radiant intensity, while providing a bit of a safe zone. Given that it's only 3 LEDs, I'd have no qualms about running them in series with one appropriately sized resistor so long as that worked properly for the application at hand. However, you do need to be aware that when one LED burns out AND dies in the shorted state OR is no longer consuming it's share of the total current, the other LEDs in the series will also be damaged. I consider this arrangement a possible problem only in the event of a premature failure, as IR LEDs tend to wear out at a fairly even rate across the board and usually quicker than other types. So just like the brake pads on either end of a vehicle, if you replace one side due to wear, you might as well replace the other because they are probably due. As for the proper wavelength, there is anecdotal evidence out there for 940nm being optimal, but to really know for sure one would need to look at not only the specs for the sensor, but also the specs for the filter material in front of it (if it has one). Ideally, the filter should be tuned to pass the wavelengths at the highest levels, which match those most favorable to the sensor. In other words, if the sensor has the highest sensitivity at 850nm, but the filter blocks 15% of light at that frequency, it will be exactly the same as feeding it unobstructed light at a frequency to which it is 15% less sensitive. So gains will be limited if the optical components are not properly matched to begin with. The issue is that these components seem to be hacks built on hacks which have little if any official specifications available, meaning that more hacking (and not just with the LEDs) might be necessary to really use them to their fullest potential. |
| pacooka:
Ugo, Zebidee, and RandyT, thank you for the detailed responses, I really appreciate it. |
| CRaccani:
Hey, JayBee Just donated to your fabulous project. When can I expect the email to access the discord etc.? Regards Thank you, all good. JB contacted me via his Discord channel. |
| Totophe:
Bonjour à tous Je suis en train de fabriquer ma borne et ce projet du gun 4ir m'intéresse beaucoup. Ma question est si je donne la contribution paypal il y a aussi la liste de pièces à commander ? En attente de votre retour bonne soirée. |
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