Glow Plug Igniter with CONSTANT CURRENT --Oz--

I read the other Glow Plug Igniter thread(s) and with my experience, I don't see a elegant/or correct/and simple solution to the problem igniting a glow plug CONSISTENTLY with multiple conditions the average pilot faces during starting of the glow motor.

A quick briefing nomenclature:
C.V.=Constant Voltage
C.C.=Constant Current

Using a completely unregulated battery at 1.5V output is crazy IMO (like a caveman in 18th century). Yes, it works when "everything" is in order (as a minimum, the current flow enough to light the mixture, but the plug maybe failed (open/short) or flooded or no fuel). A glow plug is simply a nichrome wire that heats up relative to it's current flow, and not to its voltage, this is why a C.C. circuit is more important than a unregulated voltage used by majority of the nitro pilots.

To glow the plug: battery/connector/wires/connector/plug will give various results. Why, because the low 1.5 volts output and sorta high current (couple amps) will give random voltage drops at each component in the path (different Ωs for each) and ultimately give a different current to the plug. Remember, current (not voltage) = heat.

So instead of using old school (1960's) unregulated battery voltage with varying glow plug output, (sure, a new plug, new battery, and good connector will work great). But when everything is used, you have multiple voltage drops (battery output, leads IR drops, connector IR drops), leading to random (to possible low) currents (and wattage) in the plug and starting issues.

My thinking is use a simple CV/CC dc-dc adapter with adjustable voltage and adjustable current. So simply set the voltage to say 2.0V and leave it and then limit the current to what the plug needs (E.G: 1.0 to 2.0A), if there is multiple voltage drops (battery/wire/plug-connector), they are all bypassed and the plug receives the correct current and motor starts easily.

I just need to do some simple testing, then tweak the electronics to make a decent adjustable current range (not to high or low adjustment range). I have several dc-dc cv/cc adapters that I can use to test with.

What's the highest/lowest current pilots have seen for their plug current? tia

With a integration of a V/A meter (couple bucks) and (tuned) pot (dialed in so the range is current appropriate for the plug(s) that's is used, for a high and low current range), the current could be easily dialed for each users needs, win/win, thoughts?  

https://www.banggood.com/DC-DC-CC-CV-Buck-Converter-Board-Step-Down-Power-Supply-Module-7-32V-to-0_8-28V-12A-p-1245047.html?rmmds=myaccout-bottom-alsolike__1&cur_warehouse=CN
No you dont need 12A, but that is adjustable. I am expecting around 1~3A, so something higher will work.


EDIT: 11-6-2019  With my little testing, CC "only" is not the best way, a combination of CV/CC should work well.
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11-20-2019
Testing summary of different modes:

CC Only Pros: (in other words, the glow plug is constantly in CC mode)
1. Removes all IR Losses (voltage loss across resistance causing lower plug temp), at battery connectors, wire losses and, clip on connector losses, this is its number one benefit.
2. Short circuit protection, if the clip on plug connector (or anywhere else) shorts accidently, the CC handles this issue without any issue (burning wires, arcing, melting, etc).
3. Can use any power source voltage (within dc-dc specs).

CC Only Cons:
1. CC does work well until the glow plug is flooded, it will take longer to clear if using only using CC control. Because the now colder plug has less resistance and therefore less voltage drop, even though the current stays the same, this totals up in lower power in the plug to clear the flooded plug. It still will clear the plug, but takes more time. My original thought was lasers and led's, the output is about current driven, but I was wrong with the PTC properties of the glow plug.

CV Pros:
1. A big step up over unregulated battery voltage setup, battery voltage does not matter in CV setup as output voltage is regulated, only IR drops can give inconsistencies.
Unlike a unregulated battery voltage that changes with its SOC (state of charge level), the output voltage will stay constant, this is significantly better than unregulated battery voltage. If you have good good setup (power supply connections, wire condition and clip on connector), this works well, maybe not as good in all conditions as the 10X the cost RCATS system provides.
There is a window the plug will run at (say for example 1.3V to 1.4V), but if you set the CV voltage to the higher side of this window, this clears the plug faster in a flood condition.
2. Can use any power source voltage (within dc-dc specs).

CV Cons:
1. Any IR losses in connectors/wire will lower plug voltage and temp. This can be offset a lot with remote 4 wire sensing at the plug connector.

Unregulated V Pros:
1. Very low cost, when everything is good, it works, but clearing floods will take the longest.

Unregulated V Cons:
1. As battery voltage drops, so does plug temp and also clearing a flood is much more time.

CV/CC Pros:
1. Not having to take out a second mortgage to light your plug. Can be assembled for under $12~$20 depending on the plug clip you buy, ($4 for two 18650 2600mAH cells, $4 dc-dc CV/CC buck converter, and plug clip with wires, add a $1 more for USB Li-Ion charger board, and a couple more bucks for a V/A meter if wanted), for me it was $4 as I have batteries and plug clips.
2. Short circuit protection.
3. Can use any power source voltage (within dc-dc specs).
Unlike a unregulated battery voltage that changes with its SOC (state of charge level), The output voltage will stay constant, this is significantly better than unregulated battery voltage. This can be offset a lot with remote 4 wire sensing at the plug connector.

CV/CC Cons:
1. Have to assemble (about 4 wires) and set the two pots for CV and CC settings (pretty easy), takes time (10 minutes), but time is free in hobby.
2. Any IR losses in connectors/wire will lower plug voltage and temp. This can be offset a lot with remote 4 wire sensing at the plug connector.

CR: there is a few possible ways to implement this function, couple of them are:
1. Simplest is a 4 wire (remote sense) at the plug clip connector (either 4 contacts at the connector (best, true 4 wire) or at least 4 wire sense at the plug connector) and use CV (I can see the comments coming, lol).
2. Another way is a arduino nano processor ($2) with current sense resistor and PWM drive, with the analog input, you could sense the plugs voltage (yes, this is equal to its resistance) when the PWM drive current is in the off state (with small bleeder resistor). With this, you could add extra features like, automatic turn off, 5 second delay, slow ramp up (I think are not beneficial). I would head down this route if I wasn't busy with other projects.
3. PWM drive with voltage feedback and analog control, such as the famous 555 timer and a lot of analog tweaking might be fun.

I am sure this list is not complete but it's a good start (more testing needed at the limits). Probably could use a proof read or two.

It was mentioned, "Pylon, Team Race, Speed, Combat competitors use RCATS".
It makes sense, in competition, racers are willing to way overpay to get an advantage, even if its very slight or even a placebo, EG: instead of a sport $60 esc, would pay $250 (only difference was the FET's and could not tell the difference on the track). In big races like nationals and worlds, I would guess they use a new plug every qualifying and race run, club races probably not so much. Paying 10X is probably not even thought about in competition at that level.

It would be nice to see the RCATS preformance side by side with a properly set up CV/CC setup, anyone in SoCal area?
Even a 15 second video of it clearing a 1 drop flood (hot, then 1 drop, then watch it clear the flood and back to hot). This is the only advantage I see the RCATS should have an advantage over CV/CC setup (as I dont care about auto turn off or 5 second delay features).

PS: I would like to change the thread name, but seems this forum does not allow that.