GCL-2 on-board Glow Control Logic Nyomtatás
Írta: Magi István   
2013. május 20. hétfő, 10:44

The GCL-2 on-board glow was developed after experience gained from the GCL-1 design. Adjustment of the glow threshold and power output has been simplified and it includes an integrated BEC. It is less sensitive to battery level and cabling voltage drop.

The glow eletronics were developed for single-cylinder, methanol motors. If you use multi-cylinder engines, please read GCL-3 glow control!

The main technical features:

Glow:  Uses a 3s LiPo battery with a voltage range of 9-14V.
Integrated switching power glowing BEC (max. 4A).
Lipo protection against deep discharge (disable on 9V).
Adjustable and stabilized glow voltage (0.7-1.8V).
Adjustable glow threshold (in total servo province).
Adjustable glow direction (can reverse).
Short-circuit protection.
Multi turn, vibration resistant regulatory trimmers.
LED status indication.
Servo-side control 4V – 6.6V.


You need to use a 3s LiPo battery (11.4V) to power the glow plug. The recommended capacity is 1500mAh. If you use an ordinary glow plug, it will pick up about 0.3-0.4A behind glowing from the battery (there are about 3-4A on the glow plug then). Accordingly, if you glow constantly using a 1500mAh battery, it can feed the circuit for about 3.75h. You don’t need use the glowing of motors in full throttle province, just in idle. That’s why the flight time will be significantly longer with one battery charge!

This GCL-2 provides adjustable and stabilized output voltage. The settable range is 0.7V – 1.8V. The voltage required by ordinary glow plugs is 1.2V – 1.4V. So glowing electronics which use simple 1.2V NiMh batteries, are very sensitive to the voltage output of the battery and length of cabling and connection quality! Practically, when the voltage drops they don’t provide power to the glow plug within moments of falling below the operating voltage.

The GCL-2 with its adjustable (0.7V – 1.8V) and stabilized output voltage utilizes the full battery capacity of the LiPo due to its switching BEC which has better than 90% efficiency. The circuit has protection against LiPo over-discharge If the LiPo delivers less than 9V, the GCL-2 turns off power to the glow plug.

If the LiPo is ready, it indicates with LED.  (If the LiPo LED is not on, check that the battery is a 3s or fully charged.)

(Layout of GCL-2)


LED LiPo OK. If it lights, voltage of LiPo is appropriate for glowing.
LED Glow ON. If it lights, the glowing is active.


Set Glow Level. You can adjust the level of voltage of glowing (0.7-1.8V). The output voltage increases in when turned in a clockwise direction.

Set Glow Direction. You can give the direction of glowing by changing the jumper. If you use a reversed throttle servo, you can reverse the glow range.

Set Glow Threshold. You can set the glow threshold and you can also set how long it glows upwards from the idle position.

(setting of normal glowing window)

Explanation of labels:

Motor Stop = Throttle cut position i.e. motor stops
Idle = point at which motor idles reliably
Set threshold trim = adjusted glowing threshold with threshold trimmer
Full throttle = motor maximum power
Servo position = distance of throttle
Set Glow level trim = adjust glow plug power with level trimmer
Jumper setting = adjustable window reverses with the jumper (if reversed throttle servo)
Glow level = level of glow power
Glow ON = glowing is active
Glow OFF = glowing is off

The adjustable trimmers are vibration resistant and multi-turn.


It is recommended that different batteries are used for driving the glow plug and supplying power to the receiver and on-board servos! The LiPo battery must be connected with the correct polarity and with a minimum 0.5mm2 wire.

It recommended that a main switch be used in series with the battery.

 Connect the “Glow+” output of the GCL-2 to the glow plug, and the "Glow-" output to the body of motor to complete the glow plug circuit. The wires used must be a minimum of 1mm2 to carry the current without overheating. It recommended to use short wires to minimize voltage drop.

(Heavy current connections)

You can read here one of the possible solution of connect to glowing spark plug.

(Glow plug connector is made from a pipe connector)

It recommended that the negative rail of the GCL-2 Glow output is connected to the engine body.

A complete set of glow cables is included in the GCL-2 package.

The GCL-2 can be used to the power the glow plug in two configurations.

1. The throttle servo channel with “Y” servo cable:

(Y-cable connected to receiver on throttle channel.)

This solution is the easiest and don’t need to utilize a separate channel on receiver. It can be adjusted in the normal glowing window.

(normal glowing window)

The disadvantage of this configuration is that full power is provided to the glow plug when attempting to stop the motor. This makes it harder to stop the motor.

2. Using separate channel on receiver:

This configuration uses program mixing of the throttle to an un-used channel, and permits disabling the glow driver output to stop the motor when using Throttle Cut.

(Receiver channel connected)

(programmed glowing window)

This time it is necessary to program the right glow upper and lower threshold on the radio. Then put the threshold somewhere near the middle on GCL-2 . The mixes on the radio will supply the right glow functions (on/off, engine stop).

 NB: If the glow driver does not turn off when the throttle is above, say half way, adjust the Glow Threshold potentiometer by turning anti-clockwise until the Glow On LED turns off.

Sample glow program under ER9X (for Turnigy 9X TX):

Implemented functions:
The throttle servo is placed on 3.ch, the glow is placed on 7 ch.n,
Main switch of glowing (disable/enable) : GEAR switch,
Motor cut switch: TRN switch.
The glowing is active, if the GEAR switch on and the throttle is on idling speed (The upper section of Glow envelope is adjusted with GCL-2 “Threshold” trimmer.)

The glow driver is OFF, when the motor cut is used (for more successful stopping)


motor cut:



CH7 100 CH3   GEA
    R 100 FULL !GEA


CH7 S TRN 100


The correct switch-on order:

1. Turning first receiver on,
2. Turn on main switch of GCL-2 battery!

The reverse happens off.

After the cables soldered to the GCL-2, it recommended to fix the cable to the circuit board with

a bead of heat gun glue to prevent fracture due to vibration.

Then lastly, shrink the supplied translucent sleeve over the entire panel with a heat gun.

After the installation, check the extent of glowing on the glow plug. The level is good if you see that the glow plug is glowing, but not incandescent.  Adjust with the Glow Level potentiometer.

Downloadable description: GCL2_eng.pdf

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Installation patterns:

PC-9 Pilatus:

Piper Cub:

Revised by Jeff Dowsley (Thank You!)