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The SwitchGlo Remote Glow Driver

The SwitchGlo as delivered

The SwitchGlo as delivered

Since the Align 2-in-1 was being replaced, I wanted another form of remotely operated glow driver. Sure, I could go old-school and go with a hotshot and a remote plug, but that’s not geeky enough for me. No, I wanted something on a switch. Enter the SwitchGlo.

A simple device in concept, the SwitchGlo attaches to an unused channel on your receiver and when activated, supplies 1.5v DC to the glow plug for 10 seconds. It also beeps when it’s active to let you know that the plug is getting power. The tone it emits is a bit shrill and the manufacturer advises that you can also use it as a lost-aircraft locator. There’s only one hitch to this scenario. I don’t have an unused channel on my DX7 / AR7000. What to do?

After reading the various tips and tricks available at SwitchGlo’s website, I decided that I’d run the device with a Y cable off of the same channel by which my Spartan Gyro’s gain is controlled (my DX7′s GEAR channel). This would allow me to use the DX7′s two-position toggle switch to turn the glow driver on and off. Slick.

In theory it would work, but for one issue. The way I have my radio set up, the gyro reads the ATV settings on the GEAR channel to determine what mode it should be in and what it’s gain setting should be. Anything over 50% (switch “ON”) and the gyro is in Heading Hold mode and at anything below 50% (switch “OFF”) it’s in rate mode. The SwitchGlo is the same in that it’s on when the channel is “ON” and off when it’s “OFF”. This presented a problem if I wanted to use a Y cable. The gyro would be receiving the same signal from the receiver as the SwitchGlo, meaning that the SwitchGlo would be on whenever the gyro was in HH mode. Since I fly in HH mode,¬† I needed the SG to be on when the gyro was off and vice versa There is a timer limiting the SG to ten seconds, so it wouldn’t be constantly sending power to the plug, but I’d rather it was completely off when I’m flying.

The FMA Servo reverser

The FMA Servo reverser

Surmising that there must be a gadget that would allow me to set this up exactly the way I wanted it, I did some more searching and found the FMA Direct 510SR Digi(yes, the same FMA Direct that markets the Cellpro series of chargers) servo reverser. Basically, this device takes the place of the Y cable, but with a “twist”. It has one input and two outputs just like a Y cable, but one of the outputs is reversed. In essence, one output is always the same as the input¬† (if switch = ON, then servo = ON) and the other output is the opposite of the input (if switch = ON, then servo = OFF). Have I confused you yet?

The way the setup goes, the SwitchGlo is plugged into one of the reverser’s outputs and the gyro into the other. The input of the reverser plugs into the GEAR channel on the receiver. When I’m ready to start the engine, I flick the GEAR switch off, which sends an “OFF” signal to the gyro and puts it into rate mode. The reverser changes this “OFF” signal to an “ON” signal and sends it out the other connector to the SwitchGlo, turning it on. Once I start the engine, I don’t need the SwitchGlo on, and I flick the GEAR switch back on. This turns the gear channel “ON”, switching the gyro back into Heading Hold mode, and the reverser’s circuitry again changes the other output to “OFF”, shutting off the SwitchGlo.

Dual outputs replace a Y cable

Dual outputs replace a Y cable

There are other servo reversers available, but the FMA device is very small and very inexpensive at 16 dollars + shipping. I set about interconnecting everything and testing it all out to get the plugs connected to the right pins. After a little bit of trial-and-error, I had it all worked out. This is when I found another good use for the SwitchGlo. It really should have been obvious, and I probably read it somewhere, but nevertheless, it seemed like a new discovery at the time. The SwitchGlo fires up the glow plug and emits it’s audible tone as soon as it’s turned on. If your glow plug is burnt out, you will get a broken tone, or no tone at all from the SwitchGlo. This is useful for troubleshooting starting problems caused by a blown plug. If you don’t hear a solid, steady tone, your plug is hosed and you should check it out.

This looks familiar...

This looks familiar...

One other modification I made to the SwitchGlo was the replacement of the alligator clip lead glow plug connection. The Align 2-in-1 had the same setup and I still don’t trust it. The Sullivan remote glow connector I spliced in has its drawbacks (primarily that you need a hemostat to attach it due to the Align fan shroud design) but I feel that it was a worthwhile modification. While having an alligator clip vibrate off of the glow plug in-flight isn’t really a big deal, I just don’t like the idea of having a loose electrical connector flopping around inside of a carbon fiber frame. The SwitchGlo is currently available with an alligator clip or a cotter pin-like clip. I desoldered the twist-clip from the 2-in-1, soldered it to the SwitchGlo and reattached the old alligator clip to the 2-in-1 just in case I decide to sell it.

Ground lug attached to engine

Ground lug attached to engine

The ground lug was attached to the same motor mount bolt that the 2-in-1 used (since I already had the bolt out), and the ground wire was covered with a piece of expandable sleeving in much the same fashion that the Arizona Regulator’s pin switch wire was. The SwitchGlo itself fit perfectly in the electronics box just in front of my MultiGov and was secured with velcro and a velcro strap for good measure. The velcro strap covers up the sound hole for the SwitchGlo’s buzzer, but it’s so loud that It really doesn’t matter.

Final function checks were successfully completed and the heli was ready to fly.

Next: Flight Report

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