The Arizona Heli Regulator

The Arizona is a voltage regulator specifically designed for RC helicopter use. Manufactured by Fromeco Scale Avionics LLC,  the Arizona is a very capable unit and is in use by a great many RC pilots. I’m in need of a regulator that can take a 2s LiPo input, and drop it down to 6V as that’s where I’m running my cyclic and throttle servos. The cyclic servos are JR 8717s and are very high-performance digital servos, which means that they can draw a good amount of amperage. If you’ve read my review on the Watts Up RC Wattmeter, you’ll see that I tested the amperage draw of all my servos in typical usage, and that I’m pulling a max of about 3 amps under normal conditions.

The Align 2-in-1 can handle roughly 6 amps, but that’s with a full 7.4v input. As the supply voltage goes down, so does the amperage rating of the regulator, and I would like a little more headroom. The Arizona is rated to provide around 17.5 amps when supplying 6v output. This should give me plenty of extra capacity and may even be a little overkill, but better to have it and not need it… (P.S. For those of you running 8717s or 8711s at 8v, check out the Kiwi regulator, also by Fromeco, at their website)

The ginormous heatsink

The Arizona handles the heat generated by this generous power handling capability by utilizing a computer-designed custom heatsink and an open board construction. The board itself is sealed with what Fromeco calls a “conformal coating” to prevent dirt, nitro fuel, or other harmful substances from damaging it. The whole unit is then mounted on a small plastic mount called a “cat splint” by way of rubber vibration absorbing pins. The “cat splint” is slotted to allow the use of velcro straps in fastening it to the helicopter.

In addition to its standard capability as a variable output voltage regulator (user configurable from 4.8v up to full receiver pack voltage, allowing you to run your 8717s at “8v” should you so choose), the Arizona provides a separate, non-adjustable 5v output designed to supply gyros and tail servos that require it. Currently, I have a step-down inline to my tail servo to drop the 6.0v I’m running to my receiver down to about 5v, and since this is no longer necessary, I’ll be removing it. The gyro gain and rudder servo wires (from the gyro) plug directly into the Arizona. The corresponding gyro gain and rudder leads from the regulator plug into the receiver and in addition to providing signal, they provide power from the regulator to the receiver.

The regulator I purchased had a Dean’s plug on it, but I don’t use this type of connector on my helis. The receiver packs for my Trex 600 helis all use JST connectors, and I had an extra that I’d ripped out of something or other, so I temporarily made an adapter. As I haven’t yet decided what I’m going to do about that, I’ll use the adapter for the time being. I next grabbed a spare servo pigtail and my Volt-Ohm meter to check voltages. Then I plugged the regulator into the battery and was greeted with a pair of bright, blue LEDs indicating that the device was operating.

Voltage setup rig

Plugging my voltage-test lead into the “Gyro Rudd” and “Gyro Sens” ports showed 4.95 volts output at each. These outputs are fixed and 5V should work just fine to power any modern gyro / servo combination. Once I verified that all was working properly, I grabbed a spare receiver and connected the appropriate leads from the governor. The receiver powered up properly and a test of the voltage at the pins showed 7.54v.  While still monitoring the voltage, I took a small jeweler’s screwdriver (the closest conductive object to me at the moment) and carefully shorted the voltage adjustment pins. The voltage reading started to fall. I watched it for a while and it stopped decreasing at about 4.52 V, and then started climbing again.

I also noted that pulling the screwdriver away caused the voltage change to stop rather quickly, and re-shorting the pins caused the voltage to change in the opposite direction. I took the voltage back up to 6V and didn’t let go in time, causing the voltage output to hit about 6.8V. Letting go of the pins and touching the screwdriver to them again caused the voltage to decrease. I actually overshot it a few more times before I got it settled to 6.05V.

The optional (and uber-cool) pinswitch

One final feature of the Arizona Regulator is it’s ability to work as a master switch for your receiver. The yellow pigtail on the device is where an optional “pin flag” switch is attached. If this switch is not used, the Arizona is powered up simply by plugging in the receiver pack. I chose to purchase the optional pin flag switch for two reasons. First, in order to plug and unplug the receiver pack, I need to remove the canopy and I didn’t want to have to do that. Second, the pin part of the switch has a red “DANGER REMOVE BEFORE FLIGHT” flag attached to it. Really…how cool is that?

The switch is normally open, and when the pin is inserted, it closes the circuit, which the regulator senses, and shuts off. Pulling the pin arms the system (what it really does is tell the regulator to turn on, thus powering the heli, but it’s much more fun to say “arms the system”, right?). One of the main benefits of the pin switch was pointed out to me by a Fromeco factory rep (thanks, Blake). The normally open state of the pin switch means that if the switch itself fails in flight, it will “fail open” and thus the regulator will remain powered on. It’s a great safety feature and gives a measure of peace of mind.

The switch posed a couple of easily solved problems. The main issue is the question of where to mount it. I was originally tempted to mount it in the unused hole by the motor mount where a remote glow connector would normally go. It’s free, since I’m using the SwitchGlo. Unfortunately, a test fitting of the switch into that hole showed that while it would fit, the switch body rubbed against the engine’s crankcase. It would work, but I was concerned about friction rubbing through the insulation and possibly causing electrical issues or even RF noise.

The pin switch mounted

There were also a few small holes in the CF frame just in front of the fuel tank, but they were too close to the tank. In the end, I drilled a new hole halfway between the glow start hole and the tiny hole by the tank. The switch was mounted and the wires routed towards the front of the heli. Between the switch harness and the lead from the regulator, there is plenty of wire available to mount the switch pretty much anywhere on the frame you’d want to. I made sure I mounted the switch where it would be easily accessible with the canopy on. Yes, I can be taught. I also took a few extra minutes to cover up the exposed wire with some expandable sleeve and zip-tied it to the underside of the bottom frame brace.

Regulator mounted and ready to go

I mounted my regulator on the left side of my electronics “box” where my Align 2-in-1 had previously lived. It fit, but just barely and it took a bit of wiggling to get it mounted properly. The wiring from the regulator was routed and a  reasonable attempt at neatly dressing the wires was attempted, and I was ready to connect the battery and test it out. A small bit of velcro on the back of the “cat splint” helped secure it and a velcro strap threaded through the appropriate slots in the splint and the electronics box made for a very secure mount. The rubber-bushed standoffs make for a nice vibration-resistant mounting.

Applying power to the heli resulted in everything working properly and a happy HeliGeek. I sat there for a few minutes pulling the pin and plugging it back in for no real reason other than….well, for no real reason. Just because I’m a geek and it was fun. Don’t judge me.

Next: The SwitchGlo Remote Glow Driver

OR: I don’t care about the SwitchGlo, just take me to the flight report.