The CF output voltage is 3.3V (documented) and the RRC3 output voltage from the AUX is ~7.8V (measured with my cheap multimeter so YMMV). With the RRC3 you can set the AUX output to Sync with LED - which is perfect! Hell, I use a red LED for the Perectflite CF and blue LED for the RRC3 - matches the corresponding PCB colors. With the CF's you'll need a JST 3 pin connectors (or buy one from them with LED complete). It will always be on, so constantly draw current.Ī couple of altimeters that I use regularly are the Missile Works RRC3 and Perfectflite Stratologger, and just got a couple of Perfectflite CF's with the LED output on the board. If you put the LED/resistor in series with the battery/switch it will draw current away from the altimeter, which may not be ideal - it might be perfectly fine, obviously depends. I've been playing with LED's and Altimeters for a little while now - my hearing 'aint what it used to be' and my Uncle is 元 and HAS hearing aids, so I'm trying to be helpful to him as well. So, if that makes sense to you, pick out some LEDs from Radio Shack's website or local store and then we'll work through calculating what size resistor to buy, also from Radio Shack. Power dissipated by the resistor is i^2 * R, or 0.019 * 0.019 * 470 = 0.172 watt, so a quarter watt resistor is fine. Recalculate the actual current using 470 ohms and you get 0.019 A. That's not a standard resistor size, so pick one closest to it, which is probably 470 ohms. Assuming 20 mA, or 0.020 A, and using v = i*R, we solve for R to get the value of the resistor. You'll want to get it from the package or data sheet. The remainder is 9 volts.Īnother spec for the LED is the current, marked i in the spec. Let's also assume the forward voltage drop for the LED is 0.7 volts. Let's say your new battery puts out 9.7 volts. If you're using the LED with a 9 volt battery, subtract the voltage drop from the actual highest voltage of the battery. I buy mine from Digikey, or Allied, but you probably just ought to pick up some marked extra bright from Radio Shack that have a form factor you want. Then, when the switch is on power goes to both the altimeter and the LED and resistor, which are in series.ĭoes the blister card for the first switch have a schematic of any kind?Īn LED causes a voltage drop, somewhere between 0.5 and 1 volt. The LED and a resistor must be in parallel with the altimeter. With that confession out of the way, what's the purpose of the LED? Do you want it illuminated when you power the avionics (switch on)? That's going to slightly shorten the life of the battery. I've seen a lot of successful flights using RS push button switches and only one failure. However, it's your choice to make and I'll get off my soapbox. The contacts in push button switches are held in contact by springs that allow them to bounce out of contact. Second, I'm prejudiced against push button switches specifically. First, I'm prejudiced against Radio Shack quality switches in general.
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