Obsolete capacitor replacement

[ej_flys]

Hi all,

New guy here.

I am trying to build a small RC plane Glow Plug Driver that senses the resistance across the glow plug and can sense when it is cooling down and then heat it up. I purchased one just like this and it works great but the company that made it from the UK appears to have shut their doors.

I found an old plan that was posted in one of the modeling magazines years ago and I am going to give it a shot.

The problem is one of the capacitors is now obsolete.

CAP Film 0.01uf panasonic ECQ-P1H103 P3103-ND

How does one find a good replacement?

Thank you,

[redwire]

Re: Obsolete capacitor replacement

That part is ±2% tolerance which makes it very hard to find.
I have not seen the circuit, but if a ±5% tolerance part is suitable, there are many subs. Parts with long leads:
Epcos B32529C0103 10nF 5% 63VDC
Nichicon QYX series
Kemet SMR series

[R_J]

Re: Obsolete capacitor replacement

if its not that critical maybe one of the series listed in the pdf

Or maybe this Ceramic type? C330C103G1G5TA Digikey # 399-14002-ND; or Vishay Poly, KP1830310061, BC5154-ND

[budm]

Re: Obsolete capacitor replacement

Post the circuit so we can see if it is critical or not.

[stj]

Re: Obsolete capacitor replacement

10n at 2% is not that hard to find.
https://uk.rs-online.com/web/p/polyp...itors/4147327/

[ej_flys]

Re: Obsolete capacitor replacement

Thanks for the reply.

Here is the web site with the details.

http://www.aaa.org.ag/members_only/t...ctronic_on.htm

Here is the parts list that I got from the page:

1 IC timer TI CD4541BE 296-2078-5-ND
1 IC Dual Op Amp National ic dual op amp LMC662AIN LMC662AIN-ND
1 CAP 1uf panasonic Tantalum Capacitor 1uf ECS-F1CE105KGZ P2105-ND
1 CAP Film 0.01uf panasonic ECQ-P1H103 P3103-ND
1 Power MOSFET Int Rectifier IRLZ44N IRLZ44N-DN
1 LCD RED DIALIGHT 550-0404 350-1009-ND
1 MOD FET ZETEX Inc ZUN2110A ZUN2110A-ND
1 POT Bourns 3329H-1-104 3329H-104-ND
2 Molex 03-06-2024 WM1203-ND
2 Molex 03-06-1022 WM1202-ND
4 Molex 02-06-1103 WB1001-ND
4 Molex 02-06-2103 WB1000-ND

1 Res 10hms 1/2w 1% (single cylinder version)
3 Res 10K 1/4w 5%
1 Res 100K 1/4w 5%
1 Res 120K 1/4w 5%
1 Res 3.3k 1/4w 5%
1 Res 47k ohms 1/4w 5% ???
1 Res 270 1/4w 5%
1 Res 20 ohms 1/2w 1% (twin cylinder version)

Receiver cable and plug
Power Switch
Glow Plug connector
#10 stranded wire yellow
#10 stranded wire black

[eccerr0r]

Re: Obsolete capacitor replacement

Technically, yes, it is critical; but however, I would say NO this is not a critical part.

The design of your glow plug and your particular engine requirements will add variability into the operation of the device and thus will reduce the benefit of the accuracy of the timing device.

However it's probably best to stay fairly low. 5% is fine. This is because the timing resistor is also specced at 5%, and while errors are multiplicative, you already have error and more error is not that big a deal. Just don't go 20% or something crazy like that.

[redwire]

Re: Obsolete capacitor replacement

The 0.01uF cap is for the 2 second glow plug on-timer, it is not critical 1.9-2.1 seconds ±5% is fine, besides the CD4541B IC is not super accurate either. Parts used 10k/0.01uF gives 1.88 seconds.

I looked at the circuit and there are a few other obsolete parts:
1uF 16V tantalum Panasonic ECS-F1CE105KGZ P2105-ND, substitute AVX 1uF 20V 478-1833-ND Digikey or a 1uF film cap 399-5860-ND

Potentiometer Bourns 100k 3329H-104-ND is now lead-free 3329H-104LF-ND but expensive. 3362H-104LF-ND would work too.
The LED can be anything from the junkbox.
Molex pins p/n now WM1001-ND, WM1000-ND.

If you are not using a PCB to build it, note the schematic does not show power connections for the op-amp LMC662.

[budm]

Re: Obsolete capacitor replacement

technically, yes, it is critical; but however, i would say no this is not a critical part.

The design of your glow plug and your particular engine requirements will add variability into the operation of the device and thus will reduce the benefit of the accuracy of the timing device.

However it's probably best to stay fairly low. 5% is fine. This is because the timing resistor is also specced at 5%, and while errors are multiplicative, you already have error and more error is not that big a deal. Just don't go 20% or something crazy like that.

+1

[ej_flys]

Re: Obsolete capacitor replacement

Thanks Guys for your input. I'll see what I can come up with and hopefully not smoke it. :-)

[ej_flys]

Re: Obsolete capacitor replacement

Hi all,

I'm back - I purchased all the parts but am having issues getting the LMC662 to reset the CA4541 by the diagrams.

I have a 5+ battery connected as the main source and a 1.2v battery connected for the glow plug.

What is supposed to happen is when the glow plug ignites the system will ignite if for about 2 seconds and then stop and test the impedance. If it is outside of what the Op-Amp is set for then it will ignite it again and the process loops until you shut it off.

I have attached some more detailed pages I found on the net.

Any ideas are welcome.

Thank you.

[redwire]

Re: Obsolete capacitor replacement

It's got a couple wiring mistakes in Fig. 2 and 3.

They show P3 as glowplug battery (+) but P3&P5 are connected together (on the PCB) for negative ground/common, so P3 should instead go to glowplug battery (-). P4 goes to glowplug battery (+).

Hope this is your trouble. Otherwise we will have to dig in to the circuit

[ej_flys]

Re: Obsolete capacitor replacement

Redwire,

Thank you for your review and input. I swapped the 1.2v battery leads around as you suggested and it is now working on my breadboard!!!

Thank you,

Ej_Flys

[redwire]

Re: Obsolete capacitor replacement

That's great. The last glowplugs I used were on a Cox 0.049 engine until a gust of wind caused The Great Splat.

P.S. Why do the RC modellers idle the motor ? I thought you would start them and they warm up quick, and good to go.

[ej_flys]

Re: Obsolete capacitor replacement

Redwire,

RC glow engines have a throttled carburetor much different from the COX .049 engine that just ran wide open with no real carburetor.

You start the engine (idle), taxi out (idle +) to take off, take off at full throttle, climb to altitude and then depending on how you fly you will fly around the sky at various throttle settings. Idle to loose altitude and throttle up to gain. Mid+ throttle to stay the same altitude and then idle to land. Once on the ground you may taxi back to your bench or perform a touch and go. ;-)

All due to the fact you can easily control your speed with the throttle. If you are a licensed pilot it is more like flying the real thing.

Glow engines however have an issue over a spark plug in that once the engine is started the glow plug has to remain glowing to keep the engines combustion going. Low throttle can cause the glow plug to get too cold and go out. High throttle can also cause the glow to go out due to the larger volume of cooler air coming into the combustion chamber but less likely.

The glow drivers help keep the glow plug hot even when the engine is idling. The glow drivers also help with lowering your idle RPM because it will keep the glow plug hot at a lower RPM where the glow plug would have gone out before.

I have a very nice glow driver from South Hertz Models in the UK that works great using the same principal but I think they have closed their doors. Their web site is dead. There are other products out there but they use servo signal position to ignite the glow plug not resistance and some of them use the receiver battery instead of a separate battery dedicated to the glow driver. (You never want your receiver battery to go dead).

What I hope to do is create a PCB from OshPark and then others will have easy access to build this very cool device.

I also want to add a voltage regulator so I can use a LIFE or LIPO battery and regulate the voltage to between 1.2 and 1.5 volts with enough amperage to keep the glow lit.

If I get this done I'll post some final images and details. :-)

Thanks again for your help! I really appreciate it from one electronics rookie.

[redwire]

Re: Obsolete capacitor replacement

Sounds like a fun project.

I saw guys using their "12V starter battery" as power for glowplug idling the motor and got confused. How many CID are these?

I guess it would be good to have something that can take any battery (1.2-12V) and run a 1.2V glow plug, and regulate its temperature. I think PWM would be great, and something to make it work even at 0.8V on a low battery if a boost-converter was added.

[ej_flys]

Hi - I just saw this old post. To comment. The 12 volt battery is to run the 12 volt starter as well as the glow driver but the glow driver is powered through a voltage regulator that reduces the voltage down to 1.5 volts or less. Anything higher will burn out the glow plug wire. It must be below 1.5 volts. The glow plug can draw close to 3 amps.

[ej_flys]

The final version of the RC Glow driver. Video found here: https://youtu.be/d_Pssncz9XY