chris6414
Sep 10, 2007, 12:10 AM
You know your bored when...
Today I figured I would make something to test the Dynam 30A ESC cut-off. I had an Megatech Housefly radio that no longer had a housefly to fly so I dismantled it an stripped anything worth keeping like the connectors and the gimbles and unused switches. I also removed the LED indicator board. I put the red and black lead across a 9 volt battery and noticed the color of the LEDS. Two red, Two yellow and two green. I noticed the green were very Dim, almost out at 9 Volts and it occured to me I could solder some pins on and plug it into my balance connector and ta da , home made LiPo battery gauge. When the greens get dim, it's time to land. The best part is it measures it under load. I figured I could also check to see how good my Dynam $25 30A ESC's cut-off was. New battery and off to hover a pack. The LEDS stayed bright and when I noticed them starting to dim, I figured the cut-off was coming. Sure enough, as soon as the Green leds started to go out under load, the ESC's cut-off kicked in and eased back on the power. It was a little more delayed than I would've liked as it is right at 9 volts but it worked and was soft enough for a helo. The voltage and LEDs went right back up once the power was off. Just a little extra insurance to give a visual of where my pack is at. The dimming is noticable as they start very bright at full charge. I have yet to try it in the sunlight but the LEDS stay bright until the pack starts to wind down. I will try and scrounge together some low ohm resistors to help it give a little earlier indication. I would like to see the green lights start to go out at say 9.5-9.8 volts under load. A little slower notice would be perfect but it worked as I thought it would. Even an analog gauge would be cool from an old transmitter. I know there are ones to be purchased but things are more fun for me when I make them myself. Especially when they work :p
Update: Figured the lights goind out at 9.0 was too low. A 100 ohm resistor now has the green LEDs going out at 9.63 volts under load which should be a little safer for the LiPo and will keep me from flying into cut-off.
Another thing to keep in mind. While you are calibrating your gauge, be sure to use a "stable" voltage source. I had used a 9 volt battery but it would drop once the resistor was in the circuit. A 7 Cell NiCad is perfect because it holds it's voltage and is right 9.5-9.7 Volts at full charge so you get a true Cal of your gauge. If 9.6 is too high, just run the pack down to where you need or use an adjustable power supply. ;)
Today I figured I would make something to test the Dynam 30A ESC cut-off. I had an Megatech Housefly radio that no longer had a housefly to fly so I dismantled it an stripped anything worth keeping like the connectors and the gimbles and unused switches. I also removed the LED indicator board. I put the red and black lead across a 9 volt battery and noticed the color of the LEDS. Two red, Two yellow and two green. I noticed the green were very Dim, almost out at 9 Volts and it occured to me I could solder some pins on and plug it into my balance connector and ta da , home made LiPo battery gauge. When the greens get dim, it's time to land. The best part is it measures it under load. I figured I could also check to see how good my Dynam $25 30A ESC's cut-off was. New battery and off to hover a pack. The LEDS stayed bright and when I noticed them starting to dim, I figured the cut-off was coming. Sure enough, as soon as the Green leds started to go out under load, the ESC's cut-off kicked in and eased back on the power. It was a little more delayed than I would've liked as it is right at 9 volts but it worked and was soft enough for a helo. The voltage and LEDs went right back up once the power was off. Just a little extra insurance to give a visual of where my pack is at. The dimming is noticable as they start very bright at full charge. I have yet to try it in the sunlight but the LEDS stay bright until the pack starts to wind down. I will try and scrounge together some low ohm resistors to help it give a little earlier indication. I would like to see the green lights start to go out at say 9.5-9.8 volts under load. A little slower notice would be perfect but it worked as I thought it would. Even an analog gauge would be cool from an old transmitter. I know there are ones to be purchased but things are more fun for me when I make them myself. Especially when they work :p
Update: Figured the lights goind out at 9.0 was too low. A 100 ohm resistor now has the green LEDs going out at 9.63 volts under load which should be a little safer for the LiPo and will keep me from flying into cut-off.
Another thing to keep in mind. While you are calibrating your gauge, be sure to use a "stable" voltage source. I had used a 9 volt battery but it would drop once the resistor was in the circuit. A 7 Cell NiCad is perfect because it holds it's voltage and is right 9.5-9.7 Volts at full charge so you get a true Cal of your gauge. If 9.6 is too high, just run the pack down to where you need or use an adjustable power supply. ;)