Glow Plug indicator.

[Jeffrey Cottrell 2]

Hi Guys

Going back to glow after many years electric only. Made up a plug igniter from a single NiMh cell and a plug. Working fine except it will not tell me if the plug is blown.

What I need is something simple to put in the circuit to indicate go/no go on current flowing. Working on the 'keep it simple' principle so don't really want a meter.

Any ideas?

Jeff

[Graeme White]

Following

[Martin Dance 1]

Simple remove plug from motor attach your glow igniter. Glows yellow red, replace plug in motor go fly. No glow? Plug is dead, replace or plug igniter is discharged, recharge. poor connection between plug and igniter, repair. Perm any one from 3 to get the answer. Sophisticated glow drivers produce exactly the same result. The only advantage is if your  motor is fully enclosed is you don't have to remove the plug in initially. 

[Jeffrey Cottrell 2]

Hi Martin

Obvious answer, but not quite what I was hoping for. As I mentioned, I have fitted a remote glow connector. To pull the plug out, I would first have to disconnect that.

Hoping for something a bit more user friendly.

Jeff

[Ron Gray]

LED in the circuit after the plug. 

[Andy Stephenson]

A glow plug only requires 1.2 volts and most LEDs don't light until you put more voltage than that across them. Plus the fact anything you put in circuit will drop too much voltage to light the plug. I would recommend a cheap multimeter set to ohms on the lower range to check it offline.

Alternatively any power-panel with a glow supply will have a built-in meter to tell you the current the plug is consuming. Be careful of short circuits in the plug if the element is distorted and touching the sides it will take current but won't light and still look like a good plug.

[David Hall 9]

Back when we used a 2v lead acid cell for the glow plug, I used a reed relay and an LED to indicate when power was flowing through the glow plug.  The LED was mounted in the plastic clip, so it was easily visible as I connected it.    

It uses a reed relay removed from the plastic body of a door/window alarm magnetic contact (easily available and cheap) with a few turns of wire around the glass relay (see image).    I guess that if you use a small LED, it may still visibly indicate with a low voltage battery.    You can use fairly heavy wire for the windings (only around 6) so you may not lose too much in the extra wire.  

 

 

Edited July 24, 2021 by David Hall 9

[David Hall 9]

As an alternative, you could use a pair of AAA cells and another glow clip to just check for a non-blown plug element.  

(glow clip, LED, series resistor, batteries). 

 

Better still, use a 3v lithium coin cell, it can be nice and small then.    

 

Edited July 24, 2021 by David Hall 9

[David Hall 9]

Out of curiosity, I collected together a  selection of LEDs.  The normal LEDs will not give any light at 1.3v.   

There are plenty of small bulbs that work off 1.5v, any of these would work, as would the small LED insert from one of those small LED torches that work off a single 1.5v battery.  

 

[Denis Watkins]

8 minutes ago, David Hall 9 said:

Out of curiosity, I collected together a  selection of LEDs.  The normal LEDs will not give any light at 1.3v.   

There are plenty of small bulbs that work off 1.5v, any of these would work, as would the small LED insert from one of those small LED torches that work off a single 1.5v battery.  

 

 

You can amplify the volts David, with a low cost transistor, with a published circuit, to do the job

The transistor will switch at low voltage

 

Edited July 29, 2021 by Denis Watkins

[Engine Doctor]

Look around for an old MFA glow starter box. It has an ammeter built in on the front. The ammeter will show the circuit is working OK . Replace the original nicad if its gone dead or the old 2v lead acid some were fitted with with your nimh and your away. 

A mate of  mine has a small gizmo that will power a glowplug from any battery up to 12 V . This has a led that lights when the glowplug completes the circuit. It a very small board about 40mm x 25 x5 . No name on it ! He bought it at one of the CL combat meetings he went to. A little research might find one .

[Jeffrey Cottrell 2]

Hi Guys

Thanks for all your ideas, much appreciated.

Divid.

Thanks for testing, but I don't think an led or bulb of some sort is the answer.They are basically voltage indicators, so they would tell me if my glow starter had failed, but not if the plug had blown. That really needs a current indicating device.

Denis

Interesting idea, but I notice a 3v source also connected to the transistor. Where would that come from?

Engine Doctor

I believe power panels are still available, so I could just buy one, but that's not the idea.

I have only one glow model among a fleet of electrics, so I am trying to minimise the amount of support gear I have to have for only one model.

So far, I have a glow energiser powered by a single NiMh, and both fuel pump and starter powered by a 3s LiPo spare from my electrics.

However, your post did give me an idea, more on that later.

In general, Martin, in the first post, suggested pulling the plug and looking at the filament. Obvious answer, and pretty good, except I have a home made remote glow connector, and that's a bit of a faff taking it off to remove the plug.

My efforts so far have been to de-faff this and make it easier to remove. Made some progress so far.

However,ED, your post put an idea in my mind, and google search came up with this.

Designed to fit in the model, but doesn't have to. Suggested powered by a 2s LiPo, so I could pick that up from the balance plug on my starter LiPo. Actually, wouldn't need to carry the separate glow energiser at all. Ok, not much of a burden, but every little helps.

So, if my de-faffing doesn't work, that's certainly a possibility.

Might be best to leave it there. Thanks all

Jeff

 

[Denis Watkins]

3 minutes ago, Jeffrey Cottrell 2 said:

Hi Guys

Thanks

Denis

Interesting idea, but I notice a 3v source also connected to the transistor. Where would that come from?

I

 

The source is up to 3v Jeff

The trigger voltage of the transistor is 0.6v, with 3v limit, so is a small v trigger/ switch

And the source is your Sing!e Cell, 1.2v - 1.5v

 

[Jeffrey Cottrell 2]

Hi Denis

Thanks for the clarification, but I'm still doubtful. My electronics theory is a little out of date (try 50 years) but here's what I see.

Apart from my glow energiser at 1.3v I would need to find a 3v source as well.

Ok, that could be picked off the balance plug on my LiPo.

Now, if there is a voltage from the glow plug energiser as source, that would turn the transistor on and light the led, using supply from the 3v source.

Have I got that right?

If so, that makes it a voltage detector, where I need a current detector. Many ways to check if my glow energiser is still working, what I need is something to detect a current flowing in the circuit, which tells me the plug is not blown.

Or have I got this all wrong?

Jeff

[Denis Watkins]

There is nothing out of place in your theory Jeff.

My reply was to David Hall, who had found a selection of simple leds did not light up at 1.3v

And I suggested an amplifyer in the form of a low cost transistor.

 

In the original post, you wanted to steer clear of a meter, but a 3A meter is your simplest and lowest cost solution.

If you look at a good current detector for electricians you are in the £100 ball park, because of the circuitry.

 

In our hobby, we strive for simple and less, liked you ask, but at single cell voltages we are almost handicapped because TTL ( transistor to transistor logic) and computing, has pulled component manufacture and handy microchips and components to 5v supply.

 

Going back, your simplest solution is a meter, or David Halls reed relay set up.

[Nigel R]

You'll struggle to beat the cost of that hobbyking solution.

 

Personally, I carry two glow drivers. If it doesn't start, I switch to the backup. If it still doesn't start, I most likely need to be at home to debug the thing anyway.

 

Blown plugs are a rarity for sport flyers.

 

3 hours ago, David Hall 9 said:

Out of curiosity, I collected together a  selection of LEDs.  The normal LEDs will not give any light at 1.3v.

 

Standard LED needs between 2 and 3V to light up, but they also need a current limiter of some sort to prevent them blowing (the resistor in Denis schematic will set the current to around 20mA). That said, low volt LEDs are also available.

[Jeffrey Cottrell 2]

Hi Nigel and welcome.

Much appreciate the info you and the other guys are sharing, but they all have one basic issue. They're all voltage detecting devices. Handy if you need to know if your glow driver is working, but to check for a blown plug needs a current detector.

All these need something in line on the feed wire, and inevitably involve some voltage drop. When I've only got 1.3v to play with, can't really afford that.

Closest was David with his reed switch, but that would need a low voltage led to work.

Really did like the look of that HK unit, not least because I was looking for a plug cap by itself and they were £5.50 each, even if I could get one. This unit has one attached for £8.35 all in.

Must admit I was tempted to fit one to the model itself, powered by the flight pack, but I'm sure that either you or Peter would have told me that's a bridge too far, probably rightly.

So, at the moment looking in another direction.

In the second post Martin suggested just pulling the plug out. Discounted this at first because disconnecting my home built remote glow was a bit of a faff. Now looking at making it a little less faff, and got some ideas.

Work in progress

Jeff

 

[Dale Bradly]

45 minutes ago, Cassandra said:

 

• Hunt down an RCATS glow driver.

 

This. One of those "how did I ever live without it?" products.

[Jeffrey Cottrell 2]

Hi Cassandra

so:

Glow stick - Motor is inverted so it would keep falling off

Bangood meter - Couldn't fathom out the wiring diagrams. Got one on the way anyway, could be useful.

RCATS glow driver - Did a google search. The only ones I could find come from the States, at $129.

That's more than the model cost.

Good suggestions all, thanks, but none really fit the bill.

Dale

My question would be 'how did I ever live without the $129 it would cost'.

Jeff

[Ron Gray]

Glow sticks do not fall off inverted motors as they grip the plug! A couple of years ago a flying buddy flew for 8 minutes, landed then realised he’d forgotten to remove the glow stick!

Edited July 29, 2021 by Ron Gray

[Martin Harris - Moderator]

2 hours ago, Cassandra said:

 

• Try one of these from Banggood. Needs an auxiliary supply and I suspect that it may drop too much voltage if you just want to use a subC cell to drive the glow, but worth a look,

I use one of these in conjunction with a very cheap but effective voltage dropper module ,

 

Very effective driven by an old 3S LiPo.  The current display allows me to gauge whether the plug is dry or flooded once the plug characteristics have been learnt..

 

This thread gives more details.

[Jeffrey Cottrell 2]

Hi Guys

Ron

Could well be. All I know is when I first started the engine I used a push on glow clip borrowed from a clubmate. Could have been well used and lost some of its grip, but it kept falling off even with the engine upright.

Also, once the motor has started you need to reach under the model from behind to release it. Puts your hand uncomfortably close to a 16 x 12 circular saw.

My remote has a plug sited on the fuz side behind F1 and far enough away from any whirly bits.

Martin

The name is longer than the unit. I guess you adjust the output voltage to get a healthy glow at the plug. If the meter does drop too much voltage, you can bump it up a bit.

Have I got that right?

Jeff

[Martin Harris - Moderator]

47 minutes ago, Jeffrey Cottrell 2 said:

Martin

The name is longer than the unit. I guess you adjust the output voltage to get a healthy glow at the plug. If the meter does drop too much voltage, you can bump it up a bit.

Have I got that right?

Jeff

I have it set at the minimum voltage which gives a nice dull orange glow.  Typically, at this voltage (@1.35V on the meter IIRC) a dry plug shows around 2.6A and a wet one 3.3A

[Dale Bradly]

Re RCATS unit, I was given one. That said, knowing what i know now, if it failed I would buy the same unit again. I don't know your financial position, and this post won't convince you, but if you fly glow regularly, I would argue it's worth every cent. Infinitely better value than the crappy units that comprise a single AA or sub C that always seem to be flat or suffering from poor batter contact. YMMV.

Edited July 29, 2021 by Dale Bradly

[Peter Christy]

A 5 amp meter (analogue!)! You can often get something suitable from an old car battery charger or power panel, but google will find you new ones for sale.

 

In addition to telling you if a plug is blown, it can also tell you if an engine is flooded or dry. You need a decent size scale for this - like the charger or old power panel meter mentioned above. The tiny ones on glow-sticks are nearly useless for this. And don't waste money on power panels. They are responsible for more damaged plugs than anything else!

 

--

Pete