Automatic glow plug controller

[Roog]

I have been persuaded to incorporate an automatic glow plug controller in my tethered race car. The type of thing that allows you to press a button to energise your glow plug from a small on board battery which times out after say 20 seconds, long enough to get a warmed up engine away. The thing is the only ones I have found run off 4.8V to 6V. I don't have 4.8V to 6V on board my tethered car. I can fit a 1.2V NiMH or a single or pair of 3.7V Li ion batteries giving me either 3.7V or 7.4V. A lesser number of cells would be preferable.

Any ideas of how this could be done, the less weight and space the better.

Another idea is a centrifugal switch but I've not seen any thing that might work in a small ish car.

 

[Tunedfrog]

I'm actually kind of confused as to why you would want to do this.
Using a glow plug igniter, you aren't adding any weight.

 

[Roog]

Fair question @Tunedpipe , tethered cars are tied to a central post by a wire and are free running on a circular track until the fuel runs out. The object being the fastest lap time. To start them you push them with a pitchfork like object, no clutch. So with a glowplug engine you need to apply the battery and push. One suggested method is to use a battery with a long lead, but i can foresee tangle issues and volt drop. I have been told the other, more sensible method is to have a small battery on board, push a button and you get power for 20 seconds or so. The problem seems to be that those made to work like this for helicopters for instance work off the 6V RX battery pack. I would like to avoid such a big battery.

One suggestion I was given this afternoon is to use a 1.2-1.5V battery and use a centrifugal switch to cut the power to the glow plug once the car gets up to speed on its circular track thus causing a strong centrifugal force. It might take a bit of experimentation to get the switch operation right but it would make things simple.

 

[Tunedfrog]

Thanks for the explanation. I makes sense now.
I also knew what tethered cars are, I watch them one youtube. Pretty interesting and smoking hot.

 

[Roog]

Bit silly really but there is a track 6 miles from where I live and I felt the need to join in and not to just be a spectator. I liked the simplicity but it seems to be getting more complex by the minute.

 

[tudordewolf]

I have been persuaded to incorporate an automatic glow plug controller in my tethered race car. The type of thing that allows you to press a button to energise your glow plug from a small on board battery which times out after say 20 seconds, long enough to get a warmed up engine away. The thing is the only ones I have found run off 4.8V to 6V. I don't have 4.8V to 6V on board my tethered car. I can fit a 1.2V NiMH or a single or pair of 3.7V Li ion batteries giving me either 3.7V or 7.4V. A lesser number of cells would be preferable.

Any ideas of how this could be done, the less weight and space the better.

Another idea is a centrifugal switch but I've not seen any thing that might work in a small ish car.

Glow-plug "boosters" that provide a low level of current to help with idling are not unheard of amongst R/C flyers, but those are found in radio-control models with their own onboard power. I can think of a few options for a tether-car.

How about a supercapacitor? A ~50-100F supercapacitor starting at 1.5V should provide ~15 seconds to a glow plug before the voltage drops below 1V. This would be about the size of an AA battery, "extinguishing" itself automatically. You would wire it in parallel with the glow plug so that the glow driver charges it up when you start the engine, and then it'll provide a brief supply of current after you remove that ignitor that tapers off after a few seconds.

Edit: You could see if the glow driver will run off a single lipo cell, there's a solid chance it'll be enough.

 

[tntpoof]

Your making it complex. its really easy get a glow plug ignitor no radio no added weight .plug it on gp get it started then unplug got to your designated area.

 

[Roog]

Glow-plug "boosters" that provide a low level of current to help with idling are not unheard of amongst R/C flyers, but those are found in radio-control models with their own onboard power. I can think of a few options for a tether-car.

How about a supercapacitor? A ~50-100F supercapacitor starting at 1.5V should provide ~10 seconds to a 1-ohm glow plug before the voltage drops below 1V. This would be about the size of an AA battery, "extinguishing" itself automatically. You would wire it in parallel with the glow plug so that the glow driver charges it up when you start the engine, and then it'll provide a brief supply of current after you remove that ignitor that tapers off after a few seconds.

I like your thinking @tudordewolf

i did also consider a small primary cell, but a capacitor would be less wasteful and would have no issue with high impedance

 

[fstnd]

Your making it complex. its really easy get a glow plug ignitor no radio no added weight .plug it on gp get it started then unplug got to your designated area.

. To start them you push them with a pitchfork like object, no clutch.

I can imagine a RC driving away with the ignitor

 

[Roog]

Your making it complex. its really easy get a glow plug ignitor no radio no added weight .plug it on gp get it started then unplug got to your designated area.

I did consider this, but I have not seen a car started like this, perhaps holding the rear driven wheels up and give it a helping hand launch would do? I’ve not tried it yet as the car is still being built up.

I can imagine a RC driving away with the ignitor

I guess I could plug the igniter in, tied to a brick with a long string and set the car in motion!

 

[tudordewolf]

I like your thinking @tudordewolf

i did also consider a small primary cell, but a capacitor would be less wasteful and would have no issue with high impedance

Conservatively assuming a 3A initial draw, I work out that 60F would give you ~10 seconds, 100F would give you 20, but starts to get a little chunky.

 

[Roog]

Conservatively assuming a 3A initial draw, I work out that 60F would give you ~10 seconds, 100F would give you 20, but starts to get a little chunky.

Thank you, yes I have measured the glow plug current out of the engine and it is around 3A when using a plug in 1.2v NiMH igniter
Thank you for the ideas everyone, I’ll have to try a few out.

 

[9x19]

There are 6v lithium batteries on the market, made for electronic pet collars...
They are fairy small, not sure how many discharges theyd be good for...

 

[Roog]

There are 6v lithium batteries on the market, made for electronic pet collars...
They are fairy small, not sure how many discharges theyd be good for...

Interesting idea, I might have one of those kicking about spare, thanks for the idea.

 

[Roog]

Despite designing and making two options, an electronic time delay off switch to work off a 3.7V Li ion cell and a centrifugal switch I found out that for the short duration of the tethered car run you can just connect a 1.25V Ni Mh cell for the duration of the 'start plus run' and the glow plug seems to survive!

Easy solution seems to work OK.