My parts arrived and I did a test today using the General Purpose I/O ports on the TCB with a dual channel relay module and the barrel smoke seems to work well with this setup.
These are the parts I used:
Heng Long Smoke Generator 7.4 voltsI noticed that these new smokers are being sold in both 6 volt and 7.4 volt versions. For our purposes, the 7.4 volt is preferable since you are going to power it directly from the battery which is usually a 2S lipo or 7 volt NiMH. I guess the 6 volt versions are for use with the new Heng Long boards which have a dedicated 6 volt output for the barrel smoker.
Dual Channel DC 5V Relay Switch Module for Arduino Raspberry PiThere are a million cheap relay modules available on eBay, Amazon, AliExpress, etc... Make sure to buy one that is rated at 5 volts (sometimes they sell 12 volt versions).
0.1" 2.54MM Jumper Wires Female-Female F/FThese little jumpers let us connect the General Purpose output pins to the relay module. You could also use some standard servo leads, but we only need 4 connections and of course servo leads have 3 positions so that is a little awkward.
The links to these items will no doubt break eventually but I've posted photos of these items below (first three images).
The fourth image below shows how I wired everything, and the 5th and 6th images show the settings in OP Config that I used as well as the function triggers.
Basically we are controlling two relays with the A & B outputs on the TCB board. One relay controls the blower motor, the other relay controls the heating element. Due to the way I wired the blower and heater to the relays, if the heater is turned off the blower motor can not run. When the heater is turned on the blower motor is not automatically turned on, but becomes
able to be turned on. The blower is "pulsed" briefly with a function assigned to the same trigger that I assign the Cannon Fire function to. The blower relay is connected to External Output A and the heater relay is connected to External Output B.
The particular relay module I bought actually activates the relays when the control pins are held to ground, instead of to +5 volts as we might expect. That is no problem, in OP Config we just set the outputs to Default High and then the pulse will be the opposite (held to ground). But other modules may work differently, so just experiment. Either way with the correct settings in OP Config you can get it to work.
Previously OP Config did not have an option to adjust the external output pulse times, I've added this in the latest release (OP Config and TCB firmware versions 0.93.73). Before you updated your software/firmware save an OPZ file because these changes will cause your previous settings to be erased from the TCB.
Anyway, we can now adjust the pulse time which will be the length of time the blower motor runs when triggered. I found that it really doesn't need to be very long. In the crappy video I took below, I was only using 150mS (0.15 seconds).
Other than the Heng Long smoker, the other parts are very cheap. I think the ability to turn off the heater from the radio is a good one, because unlike the exhaust smoke units which have a fan running over them all the time, this one will only have a very brief bit of air blown through when the cannon is fired, the rest of the time the heating element would just be steaming away, and I found it will even start pushing a little smoke out the barrel as the gases start to expand in the smoke reservoir. Most people aren't using the general purpose outputs for anything so this approach doesn't take away any other functionality from the TCB. It does require two Aux channels from your transmitter though.