Onboard Glow Igniter With ATtiny85

Electronic projects that are either related to the firmwares for the 9x, or simply great for radio control applications.
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jhsa
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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Mon Mar 04, 2019 1:03 pm

rcyoda wrote:
Mon Mar 04, 2019 12:58 pm
Sure it works Joao, for you and not only :). As I wrote I it is also almost ready to be used for my application. I will just skip output regulation part and focus on getting stable 1.5V there. I never had any issues with these simple one cell drivers. They always worked for me, just it is pain in the a** to plug them every time you want to start a motor...
Please do the following, plug a plug to 1.5V battery, and measure the voltage :)
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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Mon Mar 04, 2019 1:32 pm

jhsa wrote: Stable 1.5V might work for some plugs, or might not. It depends on what current the battery can supply as well..
The resistance of brand new OS no. 8 plug is 0.3ohm. So the current at 1.5V will be 5A (which is inline with my measurements, +/- resistance change due to temp change or imperfection of my clamp meter). Assuming range of 5-10A (or even bit higher) for different plugs any LiPo 2S RX pack will easily deliver.

1.5V is not only a reference for people who do not understand how electricity works. It is a reference how to design a driver, to have proper current and perfect glow without a need to calibrate it for every plug :).

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Mon Mar 04, 2019 1:56 pm

You forgot that the resistance of the plug will be completely different once it gets hot. resistance will increase.. So, 5 amperes are far out in my opinion :)
A driver is designed to be a constant current device.. What is important in this case is the current not the voltage.
Try a small 1.5V battery, and see how bright is the glow plug :)
also, measure the voltage of a 1.5V battery while is connected to the glow plug.. You might be surprised.. :)

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Kilrah
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Re: Onboard Glow Igniter With ATtiny85

Post by Kilrah » Mon Mar 04, 2019 2:12 pm

Back in the day we were using 2V lead-acid cells, the NiMH thingy came later.

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Onboard Glow Igniter With ATtiny85

Post by Daedalus66 » Mon Mar 04, 2019 2:27 pm

Plugs are (or were) made specifically for 2.0v lead acid cells, 1.5v carbon-zinc cells (such as the big old #6 cells), and 1.2v NiCd (not in those days NiMH) cells. Most of the ones available today are designed for 1.2v. I would expect that running them on 1.5v constantly would shorten their life.

But of course what counts is current. So the driver needs to be adjustable.


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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Mon Mar 04, 2019 10:46 pm

jhsa wrote:
Mon Mar 04, 2019 1:56 pm
You forgot that the resistance of the plug will be completely different once it gets hot. resistance will increase.. So, 5 amperes are far out in my opinion :)
A driver is designed to be a constant current device.. What is important in this case is the current not the voltage.
Try a small 1.5V battery, and see how bright is the glow plug :)
also, measure the voltage of a 1.5V battery while is connected to the glow plug.. You might be surprised.. :)
I did not forget about temperature. Actually I wrote exactly that it may change. Surprisingly it is not changing much, or at all when I was measuring it (as you may remember I measured 6-4A, but using clamp meter, so probably not very accurate, enough though to judge on a level of amperage).

Trying small battery makes no sense, it will not have enough power to provide current needed. Plus no battery is ideal, so no surprises on its voltage under load neither.

Again, I hear and understand what you saying about the current. Still, you also regulate voltage in your design, not even knowing what current should be and calibrating it by eyeballing the brightness of the glow. The least perfect method if I may say ;).

OS writes this on their page:

https://www.osengines.com/glowplugs/index.html
How a Glow Plug Works

Spark plugs in gasoline engines cause ignition with a spark. In nitro engines, glow plugs cause ignition with heat.

Heat is created initially by connecting a glow starter or 1.5V battery to the plug. Once the plug comes up to heat, the battery is disconnected and the heat retained by the combustion chamber will keep the engine running. Engine timing is automatic and controlled by engine rpm. Running at higher rpm makes the plug hotter and "fire" the fuel-air mix sooner. At lower rpm, the filament cools and the plug fires less frequently.
There is also interesting read on Wikipedia:

https://en.wikipedia.org/wiki/Glow_plug_(model_engine)
To start a glow engine, a direct current (around 3 amps and 1.25 to 2 volts, often provided by a single, high current capacity rechargeable NiCd, NiMH or lead-acid battery cell, or a purpose-built "power panel" running on a 12VDC source) is applied to the glow plug, initially heating the filament. (The name 'glow plug' comes from the fact that the plug's filament glows red hot.) The engine is then spun from the outside using a manual crank, built-in rope-based recoil starter, spring-loaded motor or purpose-built electric motor, or by hand, to introduce fuel to the chamber. Once the fuel has ignited and the engine is running, the electrical connection is no longer needed and can be removed. Each combustion keeps the glow plug filament glowing red hot, allowing it to ignite the next charge, thus sustaining the power cycle.

Lead-acid battery cells that are used to ignite a model engine glow plug, due to their two volt output when freshly charged, usually cause a regular 1.5 volt glow plug to burn out instantaneously, and either a resistor of the proper value and wattage, or a high-power germanium transistor's base/emitter junction (in a series connection with one of the plug's terminals) can reduce the lead-acid cell's voltage to a suitable 1.5 volt level for engine starting.
Seems glow plugs are designed to be started with 1.5V and then no calibration nor current control circuitry is really needed.
Last edited by rcyoda on Tue Mar 05, 2019 7:33 am, edited 2 times in total.

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Mon Mar 04, 2019 10:52 pm

Kilrah wrote:
Mon Mar 04, 2019 2:12 pm
Back in the day we were using 2V lead-acid cells, the NiMH thingy came later.
Right, technology limits of the time :). From what Wikipedia says 2V was too high and needed to be brought down to 1.5V.

Lead-acid battery cells that are used to ignite a model engine glow plug, due to their two volt output when freshly charged, usually cause a regular 1.5 volt glow plug to burn out instantaneously, and either a resistor of the proper value and wattage, or a high-power germanium transistor's base/emitter junction (in a series connection with one of the plug's terminals) can reduce the lead-acid cell's voltage to a suitable 1.5 volt level for engine starting.

Daedalus66 wrote:
Mon Mar 04, 2019 2:27 pm
Plugs are (or were) made specifically for 2.0v lead acid cells, 1.5v carbon-zinc cells (such as the big old #6 cells), and 1.2v NiCd (not in those days NiMH) cells. Most of the ones available today are designed for 1.2v. I would expect that running them on 1.5v constantly would shorten their life.

But of course what counts is current. So the driver needs to be adjustable.
If Wikipedia is correct, plugs were't made for 2V. It was rather a problem with batteries back there. See my previous post and above here.

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Re: Onboard Glow Igniter With ATtiny85

Post by Daedalus66 » Tue Mar 05, 2019 1:01 am

Plugs certainly were made for 2v, but we’re talking quite a few years ago.


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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 1:16 am

Ok, then feel free to design your driver with a voltage regulator as you said somewhere above, and see if it works. You will have to adjust it to your plug.. then connect It to an RC switch so you are able to control it with your radio..
Please post your results.

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 1:29 am

jhsa wrote:Ok, then feel free to design your driver with a voltage regulator as you said somewhere above, and see if it works. You will have to adjust it to your plug.. then connect It to an RC switch so you are able to control it with your radio..
Please post your results.
Will do Joao. Will rather use switching voltage regulator, as you do, just focus on 1.5V on its output with no manual calibration or adjusting to any particular plugs. It should work with all glow plugs currently on the market.

Anyways, thanks for inspiration. I have learned a lot during this discussion :).

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 1:34 am

Please let us know how it worked..

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 1:37 am

Just one more thing, those glow starters with battery never worked well with my engines.. After I built the power panel for my flight box, never had a single problem, apart from the engines being stubborn once in a while of course :)

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Re: Onboard Glow Igniter With ATtiny85

Post by Daedalus66 » Tue Mar 05, 2019 4:43 am

rcyoda wrote:
jhsa wrote: Will rather use switching voltage regulator, as you do, just focus on 1.5V on its output with no manual calibration or adjusting to any particular plugs. It should work with all glow plugs currently on the market.
:).
All the modern plugs I know of are designed for 1.2v. I’m not saying they won’t take 1.5v, but they will probably last longer if not fed excessive voltage.



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Re: Onboard Glow Igniter With ATtiny85

Post by Daedalus66 » Tue Mar 05, 2019 4:53 am

jhsa wrote:Just one more thing, those glow starters with battery never worked well with my engines.. After I built the power panel for my flight box, never had a single problem, apart from the engines being stubborn once in a while of course :)

João
The problem is that the glow starter batteries are often too small and/or in poor shape. They are usually 1.2 Ah and work well initially when freshly charged but lose capacity and develop high internal resistance as they age.

I use a big fat D size 5 Ah NiCd which lasts for weeks and fires up engines reliably. In other words, it puts out current like your power panel!



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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 5:05 am

Daedalus66 wrote:The problem is that the glow starter batteries are often too small and/or in poor shape. They are usually 1.2 Ah and work well initially when freshly charged but lose capacity and develop high internal resistance as they age.

I use a big fat D size 5 Ah NiCd which lasts for weeks and fires up engines reliably. In other words, it puts out current like your power panel!
Now when you wrote it, I can actually also confirm. Initially I got cheap one and have had issues. Did not remember, as I bought better one quickly and used that one for a while, but had the same!

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 10:36 am

Nothing worse than going to the field, engine being too stubborn to fire, and then after one hour if trying you finally find out that along with the wrong carb setting, your glow starter is also not working well, or the glow plug got bad.
So, power panel all the way :) at least I can see when, and if the plug is glowing by looking at the meter. The only time the glow starter is good is to keep it in your pocket in case the engine quits at the flight line.

And , all that I have mentioned above is the reason why I built my glow plug driver. You see, it is not only a driver, but also a.part of some other system. It has a voltage sensor that connects to a receiver for monitoring the onboard glow battery, or in my case, it connects to an oXs (openXsensor). The oXs also measures the voltage at the plug. If the voltage is close to zero, the plug is working, if it is battery voltage, the plug is open, or bad.. :)
Like this, even if it goes bad in flight and the engine still runs intil it stops, I will know.

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 10:46 am

jhsa wrote:
Tue Mar 05, 2019 10:36 am
Nothing worse than going to the field, engine being too stubborn to fire, and then after one hour if trying you finally find out that along with the wrong carb setting, your glow starter is also not working well, or the glow plug got bad.
So, power panel all the way :) at least I can see when, and if the plug is glowing by looking at the meter. The only time the glow starter is good is to keep it in your pocket in case the engine quits at the flight line.

And , all that I have mentioned above is the reason why I built my glow plug driver. You see, it is not only a driver, but also a.part of some other system. It has a voltage sensor that connects to a receiver for monitoring the onboard glow battery, or in my case, it connects to an oXs (openXsensor). The oXs also measures the voltage at the plug. If the voltage is close to zero, the plug is working, if it is battery voltage, the plug is open, or bad.. :)
Like this, even if it goes bad in flight and the engine still runs intil it stops, I will know.
Problem with the first one I had was that it had some cheap battery, which coudn't keep the voltage over even a week. Once I got branded one it was fine. But ultimate solution for me is on-board driver, powered from RX battery, with a button. You press it when needed, it runs for 30 secs so you can start the engine and done, until next time you need to start the engine :). No separate battery means that you cannot forget to charge it and also less weight.

I'm not sure if I got it right about voltage sensing / detecting bad plug. You keep your glow plug powered all the time, like during whole flight?

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 11:28 am

Well, that is the idea. Specially on four stroke engines I keep the plug ON when the engine is at idle and a little above. Plug turns OFF at about 1/3 throttle.
I don't know what radio you use, but mine has telemetry and I can program logic on it. This means that I can program it to detect if the plug is good or bad only when the driver is ON. If the plug is damaged the radio will speak to me, telling me poltely to replace the glow plug.. :)

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 11:36 am

jhsa wrote:Well, that is the idea. Specially on four stroke engines I keep the plug ON when the engine is at idle and a little above. Plug turns OFF at about 1/3 throttle.
I don't know what radio you use, but mine has telemetry and I can program logic on it. This means that I can program it to detect if the plug is good or bad only when the driver is ON.
I fly helicopters, where most of the flight you use high rpm, run by governor to keep constant rotor speed. You put it on idle only when auto-rotating on when already on the ground :). In heli you don't glow the plug even on idle... at least I don't know anybody doing that. Interesting anyhow.

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 12:14 pm

Those are 2 stroke engines.. this system is more needed in 4 stroke engines when the fuel ignites every 2 rotations.. This allow for the plug to cool down at idle and the engine could stop..

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 12:19 pm

I guess this is one of a reasons we have slightly different approach to the design of this thing :).

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Re: Onboard Glow Igniter With ATtiny85

Post by jhsa » Tue Mar 05, 2019 3:17 pm

You don't even need it controlled by the radio then. You just need a switch on the copter itself.. Just don't forget it ON.

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Re: Onboard Glow Igniter With ATtiny85

Post by rcyoda » Tue Mar 05, 2019 9:37 pm

I will add one, because it is easy to do and hardly make the thing more complex or expensive... but you are right, I have remote ports on my commercial drivers and I’m not using them at all.


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