Expert Multi Cylinder Glow Driver

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Vixen

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I'm trying to get my Seidel ST540 five cylinder radial engine back up and running with all the original equipment.

I came fitted with an "Expert, Multi Cylinder Glow Driver". Over the years The single page instruction leaflet has become lost.

It's a long shot, but does anyone happen to have a copy of the "Expert, Multi Cylinder Glow Driver" instruction leaflet???

Mike
 

petertha

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Hmm, now you have me wondering what the Expert glow driver module was all about. Some dated chatter on other RC forums but not too many pictures of the igniter itself. First link shows what I suspect must have been what the module replaced (old school harness with 'suitable' battery ala OS radials). I'm curious because I'm on the home stretch of my Ohrndorf 5 radial & just about to cross that bridge now.

https://seidel-engines.com/wp-content/uploads/2021/01/SeidelTriebwerke_ST-770_manual_eng.pdf
Seidel history - Seidel Engines
https://seidel-engines.com/wp-content/uploads/2021/01/SeidelTriebwerke_ST-540_parts_en_1994.pdf
Seidel radial engines - RC Groups
 

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petertha

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I suspect you want to use the system you have, but if push comes to shove, this igniter module is available on your side of the pond. My (more electrically savvy) friend tells me that if space isn't a concern, he could recommend some suitable AliExpress adjustable 2V/5A regulators that can accept a broad range of input voltage levels, for example a common RC Lipo/Life battery. But I'm getting ahead of myself. Theoretically I could adjust each one individually which could be beneficial.

 

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Vixen

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R
Thanks again petertha,

Yes, I would like to use the original equipment to run the engine.
The Expert multi connects a 2.2volt battery to the five glow plugs when the throttle is closed. As the throttle servo is opened above a per-determined level; the glow power is removed and reapplied again when the engine is throttled back to tick-over. So the Expert Multi is all about keeping the glow plugs alive at low speeds.

I discovered the Expert Multi was also sold under the World Engines badge and I have found a photo of the instruction leaflet. So all is well.

The next problem is my big 25Ah Cyclon single cell, lead acid battery has died and will no longer accept a charge. So a replacement large capacity battery is also now required. And they are not cheap ($100 ish).

Five glow plugs need a lot of current, 8 to 10 Amps, which means a large capacity battery; whatever the voltage or whatever glow driver you decide to use.

Mike
 

petertha

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Here are my thoughts (always dangerous LOL). We don't necessarily need a 'large capacity' battery, but we do require a battery of sufficient C-rating. Almost any low cost RC Lipo pack these will easily handle the current requirements. Just using this $26 example, 5000maH capacity rated at 20C yields 100A. That's C-continuous so 8-10A wont even tickle it. At a load of 2v * 10A = 20 watt-hr, this pack would yield 1.8 hrs continuous running less the usual losses. The issue is the nominal voltage of Lipo chemistry: 3.7v/cell is a mismatch to ~2.0V glow plug. So that entails some kind of step down voltage regulator(s) that can accept this elevated input voltage, and deliver at ~2V and be rated for at least 2A (although I've read that glow plugs can draw 4A+ in certain conditions so best to have more headroom).

Older gen lead acid, NiCD & NiMH have a closer match to glow plug voltage levels but significantly lower C-rating. So you needed much bigger capacity in order to deliver the total amps. I've seen some glow plug driver circuits intended for airborne RC using lightweight rechargeable packs, but I don't have the ability or desire to make my own boards. So that's why I'll likely go down the path of 5 el-cheapo regulators, one dedicated to each plug. Turning them on & off like you mentioned via RC TX at some defined throttle position should not be too difficult, but I suspect a switching do-dad is required which I'm drawing a blank right now. Its used in robots a lot for larger for controlling larger amp draw devices but not as common in conventional RC.

Lets stay connected, maybe there are synergies to our applications. I've still got inventory of NiMH round cells so that might be an option for me too.
 

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DiegoVV

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Here are my thoughts (always dangerous LOL). We don't necessarily need a 'large capacity' battery, but we do require a battery of sufficient C-rating. Almost any low cost RC Lipo pack these will easily handle the current requirements. Just using this $26 example, 5000maH capacity rated at 20C yields 100A. That's C-continuous so 8-10A wont even tickle it. At a load of 2v * 10A = 20 watt-hr, this pack would yield 1.8 hrs continuous running less the usual losses. The issue is the nominal voltage of Lipo chemistry: 3.7v/cell is a mismatch to ~2.0V glow plug. So that entails some kind of step down voltage regulator(s) that can accept this elevated input voltage, and deliver at ~2V and be rated for at least 2A (although I've read that glow plugs can draw 4A+ in certain conditions so best to have more headroom).

Older gen lead acid, NiCD & NiMH have a closer match to glow plug voltage levels but significantly lower C-rating. So you needed much bigger capacity in order to deliver the total amps. I've seen some glow plug driver circuits intended for airborne RC using lightweight rechargeable packs, but I don't have the ability or desire to make my own boards. So that's why I'll likely go down the path of 5 el-cheapo regulators, one dedicated to each plug. Turning them on & off like you mentioned via RC TX at some defined throttle position should not be too difficult, but I suspect a switching do-dad is required which I'm drawing a blank right now. Its used in robots a lot for larger for controlling larger amp draw devices but not as common in conventional RC.

Lets stay connected, maybe there are synergies to our applications. I've still got inventory of NiMH round cells so that might be an option for me too.


Your train of thoughts is not correct. The C rating is the peak in Amps that the battery is able to deliver. The capacity in this case is 5000mAh or 5Ah, it means that it has enough stored energy for delivering 5 Amps for an hour, 10 Amps for 0.5 hours or 2.5 Amps for 2 hours.
 

Vixen

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petertha

Do you know of any 3.7v to 2.0 volt DC DC converters, capable of at least 10 amps??

Also need to consider the intermittent use of a model engine. In a years time, the chosen battery will have reduced in capacity due to storage etc; so you would be advised to start off with a 'larger capacity' than the theoretical size.

A single cell Gates Cyclon rolled lead acid battery makes perfect sense; either two smaller 8Ah or a big 25Ah cell. Nicads are more trouble than they are worth. Nothing spoils the fun like a flat battery

Mike
 

petertha

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Your train of thoughts is not correct. The C rating is the peak in Amps that the battery is able to deliver. The capacity in this case is 5000mAh or 5Ah, it means that it has enough stored energy for delivering 5 Amps for an hour, 10 Amps for 0.5 hours or 2.5 Amps for 2 hours.

Maybe you are misunderstanding. I'm just saying that this example battery can handle substantially more current than the anticipated level of 8-10A, not that it will operate at this level. Just do some Googling for how C-rating is calculated. It is a very common way to compare a batteries ability to deliver current as a function of its capacity.
.

 

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petertha

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Do you know of any 3.7v to 2.0 volt DC DC converters, capable of at least 10 amps??

No, but I was made aware of some that are in the 2-5A range, hence my plan to have 5 of them, one dedicated to each glow plug but feeding off a common battery. Sounds wasteful, but they were spit cheap. They are also somewhat programmable so for example the lower plugs could be set a bit warmer than the uppers. I'm not at my correct computer right now but I will endeavor to find the links my friend sent. They were AliExpresss specials.
 

petertha

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This may or may not have been the unit recommended to me. It seems similar. There are fancier ones out there with digital display & programming capabilities.
Attaching screen grabs in case the link doesn't work. If anyone thinks I'm barking up the wrong tree let me know, sparky stuff is not my forte.

 

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bluejets

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I built my own for the four cylinder using an ATtiny85 module and mosfet.
 

petertha

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Thanks @bluejets I don't want to impose on Vixen's post but did you discuss your glow driver design or show a schematic somewhere on the forum? I'd like to refer it to my electrical engineer friend because not at all familiar with what the components do.
 

DiegoVV

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Maybe you are misunderstanding. I'm just saying that this example battery can handle substantially more current than the anticipated level of 8-10A, not that it will operate at this level. Just do some Googling for how C-rating is calculated. It is a very common way to compare a batteries ability to deliver current as a function of its capacity.
.

In your own words..."5000maH capacity rated at 20C yields 100A. That's C-continuous so 8-10A wont even tickle it. At a load of 2v * 10A = 20 watt-hr, this pack would yield 1.8 hrs continuous running ".....Not correct
I don´t have to google this, being an electrical engineer for more than 20 years I know one thing or two about the topic.
 

petertha

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Your train of thoughts is not correct. The C rating is the peak in Amps that the battery is able to deliver. The capacity in this case is 5000mAh or 5Ah, it means that it has enough stored energy for delivering 5 Amps for an hour, 10 Amps for 0.5 hours or 2.5 Amps for 2 hours.

OK, lets delve into this some more. I'm willing to learn! LOL I'm going to paste a YouTube video which discusses battery terminology in some some detail. I think I comprehend it correctly, but maybe I didn't express myself correctly in the post. Because I think what you described above is an idealized battery, all discharge scenarios equal 5 amp-hours. But that ignores battery chemistry where capacity is reduced as a function of elevated discharge amperage rate.

Here is the (long!) video. First off, do you agree with it?

 
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petertha

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At 38:19 he shows a plot of a 12 volt, 7 amp-hr battery at various discharge rates, 3.5A (0.5C), 7.0A (1C), 14A (2C). The resultant capacities of these discharge scenarios do not equal the nominal capacity of the battery. Nominal rated = 12V * 7 amp-hr = 84 watt-hr. The 0.5C = 42.7 W-hr = 51% capacity, the 1.0C = 34. W-hr (41%), the 2.0C = 28.9 W-hr (34%). And the resultant discharge run times similarly decrease. I think its safe to say this is probably a lead acid although maybe I missed if he mentioned.
 

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petertha

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Where I am going with this? Now it gets a bit harder to describe but I want to compare lead acid chemistry to Lithium because they have different discharge curves. For example this comparison plot shows at 12.0v cutoff, the lead acid can only deliver ~45% of its rated nominal capacity vs Lithium can deliver ~93%. The higher the threshold voltage, the bigger the difference in favor of lithium. So isn't Lithium better in terms of requiring less Amp-hr capacity?

Now for driving glow plugs I admit I am on uncharted waters here because the individual plugs require specific voltage & current levels that don't match these nominal battery voltages neatly. But if I assume a plug requires 2.0v somewhat like @Vixen single cell example, isn't that equivalent to 12V equivalent on this battery example on a comparative basis? The problem of course is how do I make a 3.X volt lithium cell match my 2.0v plug requirement?
 

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Vixen

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As Hamlet said ‘There are more things in heaven and earth, Horatio, / Than are dreamt of in your philosophy.’
A glow plug is heated by the current flowing through it's platinum wire coil. The exact current depends on the applied voltage and the make of the glow plug. The platinum wire coil needs to be heated between dull red and bright orange in order to start your engine, Any hotter, (white) and you risk burning out the platinum wire coil. The required heating current is achieved by applying a voltage, between 1.5 volts and 2.0 volts, again dependent on the make of glow plug. You can therefore draw your horizontal lines any where between 12 volts and 9 volts. So the sealed lead acid Gates Cyclon is still a good choice and it does not suffer the risk of catastrophic failure if discharged too deeply.

The Expert Multi Cylinder Glow Driver, in addition to switching off the electrical supply at higher throttle opening, also regulates the current flowing through the glow pugs. There is a switch which allows you to apply full battery voltage, for a short time, to clear any oiled glow plugs.

The biggest problem, as you say, is how to make a 3.6 volt lithium cell match the 2.0v plug requirement. You talk about using 5 Amp 'cheepo' step down converters, perhaps one per glow plug. Have you actually studied the working characteristics of these devices??. I know that's going to be difficult as the Chinese only publish the headlines. Input volts 5v to 32v; output volts 0.8v to 30v, maximum current 5 Amps. etc.

I found a test report for a much bigger SZBK07 300 Watt, 20 Amp step down converter, which uses a similar technology. The test report was instructive, as it shows the performance trend with different input output voltage combinations. The test results show that at the top end of the input and output voltage ranges, the SZBK07 step down converter could deliver the high currents Viz, 30 volts input and set to regulate a 15 volts output; the current will be limited to 12 Amps.
However as the input voltage approaches the lower end of the range, the available output current drops off significantly. With a 9 volts input and set to regulate a 3.3 volt output; the current is limited to a mere 5 Amps. You can deduce that at even lower input voltages (3.6 v) the available current will drop even further. And all this from a step down converter 'Chinese' rated at 300 Watt, 20 Amp.

I still maintain, a single cell Gates Cyclon rolled lead acid battery makes perfect sense. I cannot say the same for a Lithium Ion battery

Mike
 
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petertha

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Thanks Mike. I wish I had a firmer gasp of DC regulators. I will consult my electrical engineer friend. I'm not concerned by airborne weight so may go at it with round cells, at least to make some initial smoke.

Here is the the OS-5 cyl writeup. Actually quite simple as long as the appropriate battery is used. I have heard on forums that the wire harness (gauge) and length make a difference.
 

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