GoNavy

My Feedback: (15)

I would appreciate suggestions on how to provide for a dedicated battery to the receiver. I fly 72 MHz Airtronics with analog servos. I use 4.8 volt receiver packs.

I recently found time to check current loads and voltage drops in the typical battery/receiver/servos airplane setup. I was surprised at the current requirments of servos; For example, the 94102 Airtronics servo (rated for 50 oz/in torque) will draw 4.5 mA at idle, 190 mA at 50% load, 410 mA at 100% load and if stalled, 520 mA. My Midwest AT 6 has 8 servos for the flying surfaces (including flaps), plus throttle and retract switch servos.

I am not sure of the voltage required to the receiver for proper operation, but surmise it to be 4 volts. I judge that a flight with the on board packs at, say, 5.0 volts, could result in voltages at or below 4 volts with two or three servos under a significant load.

I realize that one could simply add pack capacity, but want to consider the option of a pack dedicated to the receiver which I believe only draws about 30 mA.

How does one wire for a separate battery dedicated to the receiver, with another (or others) serving only the servos? Is there a commercially available device to make this simple? Is this device from Servo City what I need:
http://www.servocity.com/html/servo_power_boards.html

Rodney

Yes, that will do it. It is not to hard to make your own but it will probably not look as neat and organized as the commercial units. Your concern is very pertinent, even more so for those using 2.4GHz units as a voltage drop, even for just a few microseconds, can cause the receiver to reboot (these are small computers, not just receivers) and cause loss of control for a few secondsmaybe as long as 20 or 30which can result in some very undesireable results. Using such a device allows you to power the receiver seperately always keeping adequate voltage there to prevent data loss or drop outs.

GoNavy

My Feedback: (15)

Rodney:

Thanks. And one follow up question please:

I am a fan of redundancy...two packs, two switches. I could add two instead of one for the receiver but does anyone do this: One pack just for the receiver but also an electronic device, such that when the voltage from the receiver only pack falls below a preset limit the device connects the receiver to the servo battery packs, thus keeping the receiver supplied till the end of the flight?

Ram offers the "battery backer". The dual battery and switches connect to the backer. It allows the plane to draw only from the "primary battery" until it "senses a momentary load glitch to approximately 4.1 volts". At that point the back up battery "shifts from the no drain mode"; I take that to mean that it disconnects the primary battery and connects the back up battery. When this occurs, a red light comes on to alert the pilot to the issue.

The side of my AT6 is starting to look like an Allen Bradley control box with switches, charge jacks and other items ( the 2 mains, 1 glow driver, 1 pack for smoke pump and adjustable pots and three way switch for the twin glow drivers).

tpascoe

For those interested in the redundant supply questions, and the possibility of running at something higher than 4.8 volts steady, check out the Tech-Aero tips PDF for explanations.

http://www.tech-aero.net/documents/Tech-Tip%200601.pdf

My understanding is that the Balanced and Hot Standby configurations can be done without the regulator, assuming 4.8v packs to the receiver of course. The Tech-Aero regulators have a very good reputation in the patterm community. I have no affiliation with Tech-Aero - this is just a pointer to more resources [8D]

http://www.tech-aero.net

Tim