1.5 volt regulator @ 6 A

[Ted61]

I am using a Nelson dual plug electronic glo lighter in a new aircraft and would like to use a spare 11 volt LiPO to power it. Therefore, does anyone have a suggestion as to which regulator I might use. Preferably in a 220 package which I'll heat sink. Thanks. Input 11-12 V, output between 1.2-1.5V at 6 amps intermitantly.

[rick.benjamin]

Deleted, see my updated post below:)

[Ted61]

Thanks for the help, Rick. However, either regulator will only give me 3A of output. I'm pretty sure 2 glow plugs will pull more than that (the engine's a twin). Any info on a 1.5 v regulator that'll give me 4-6 A? Thanks!

[Ron W3FJW]

Parallel two of them with low value equalizing resistors on each output to the common plus.
Don't forget to add a .1 cap on each one.

[F-111 John]

or make a dual output circuit, with one regulator feeding each glow plug.

[jeffs555]

Current rating is only half the story, and power dissipation is usually the limiting factor for a linear regulator. Even if you could get a linear regulator rated for that much current, the power disipation in the regulator would be about 60 watts and a TO-220 package won't handle that much power. You generally need to keep the junction temp below 125C and a TO-220 has a Tjc(thermal resistance junction to case) of about 3degC/watt. At 60 watts the junction will be 180C above the case temperature. On a normal day even with an infinite heat sink the junction would be over 200C.

You would be better off using a switching regulator or just using a NICAD or NIMH.

[rick.benjamin]

http://www.nelsonhobby.com/electr.html
I agree you need a 1.2v 2000mAh nicad to power your system.
Here's a perfect deal
http://www.batteriesamerica.com/
Or you can find the same thing at a local camera store, etc

[rich smith]

It is absolutely ridiculous to knock 12.6v down to 1.2v at 6a with a linear regulator. A cheap UBEC switcher makes sense or, if you insist on DIY, build one from scratch.

I am using a Nelson dual plug electronic glo lighter in a new aircraft and would like to use a spare 11 volt LiPO to power it. Therefore, does anyone have a suggestion as to which regulator I might use. Preferably in a 220 package which I'll heat sink. Thanks. Input 11-12 V, output between 1.2-1.5V at 6 amps intermitantly.

[phil_g]

It is absolutely ridiculous to knock 12.6v down to 1.2v at 6a with a linear regulator.

Totally agree. If its just for glowplug power, a simple 555 set to 10:1 pwm with a good switching mosfet & jobs a good 'un with no heat problems.

Phil

[rich smith]

Totally agree. If its just for glowplug power, a simple 555 set to 10:1 pwm with a good switching mosfet & jobs a good 'un with no heat problems. Phil

Ah yes... 555, "The Chip That Will Not Die!".

Actually for glo cheap NiCd or NiMh as mentioned makes most sense. Few Walmart AAs in parallel.

[F-111 John]

Totally agree. If its just for glowplug power, a simple 555 set to 10:1 pwm with a good switching mosfet & jobs a good 'un with no heat problems.

Phil
A glowplug has very low cold filiment resistance. I wonder if the inrush current wouldn't destroy the MOSFET?

Back in the olden days, they used to simply rig a D-Cell to a microswitch. The throttle servo would activate the microswitch at a preset throttle setting (usually close to idle) and disconnect at cutoff or at greater than 1/4 throttle.

By the time you build all the electronics and add the lipo, you're probably over the weight of a D-Cell anyway.

Ooh! Like this! http://www.rivercityradiocontrolledflyers.com/tips.html

[F-111 John]

here is an interesting idea. I found this old RCGroups thread http://www.rcgroups.com/forums/showpost.php?p=1237894&postcount=7 which led me to this website http://electrodynam.com/rc/EDR-103/index.shtml which led me to this schematic http://electrodynam.com/rc/EDR-103/schematics.html

In short, connect the two glow plugs in series, use 3 volts at 3 amps. Much more doable with either two D-Cell NiCds, or with your original lipo/regulator idea.

[Gwest]

How do you connect two plugs in series? They have a common earth, the engine.

[Rodney]

How do you connect two plugs in series? They have a common earth, the engine.
One lead goes to the the top of first plug, other lead goes to top of second plug. Both are now in series if you power the two leads (one on each of the plugs). Nothing connects to the engine frame.

[jeffs555]

The OP said that he was using a Nelson electronic igniter( http://www.nelsonhobby.com/electr.html ) so he would probably need more than a simple 10:1 pwm circuit. Don't know how the igniter uses the 1.5 volt supply so there is the possibility that simple pulsed 12v might kill it.

[phil_g]

How do you connect two plugs in series? They have a common earth, the engine.

Not unless its a metal airframe!

Edit: sorry just realised, its a twin cyl engine, not a twin engine plane.
So ignore the two-engine drawing below, just wire to each plug tip, ignore the engine body.

2nd Edit: Dang! beaten to it by F111 :)

[F-111 John]

Even if it is a twin, or two engines with a metal airframe, you can connect the plugs in series.

[jeffs555]

Don't know much about glow plugs or how often they fail, but seems to me that on a twin engine plane wiring both plugs in series would eliminate some of redundancy you get with twin engines. If one opened up, neither would work.

[phil_g]

Don't know much about glow plugs or how often they fail, but seems to me that on a twin engine plane wiring both plugs in series would eliminate some of redundancy you get with twin engines. If one opened up, neither would work.

Good point Jeff, but you shouldnt lose the engine... I've never had an engine stop because the plug element went o/c mid-flight, it should continue to glow for that run... dis plugs are usually found when you cant get a glow on the next start... my humble findings of course...

[F-111 John]

Phil's right. This glow circuit is insurance against the engine stalling at low RPMs, but is by no means required for flight. 99% of glow engines have no onboard battery system for the glow plugs at all.

If one glow plug opened up, that cylinder would most likely stop working because either the coil breaks off or compresses itself and no longer sustains a glow. The other plug will chug along as if nothing happened, but just won't get the extra juice at low RPM.

[Rodney]

The technique of using PPM (approximately 1 millisecond full 12 volt followed by 9 to 11 milliseconds of no voltage) works very well. That is how all the power panels work that run off your 12 volt field box battery. The little pot you twist varies that "off" time by adding or shortening that 9 to 11 millisecond part of the pulse.

[Ted61]

I appreciate all the interest this has generated. I emailed Jerry Nelson of Nelson Electronics regarding my problem. Just for everyone's FYI, he suspects the switch I am using can't handle the current being drawn by the electronic glo lighter, thus, dropping the voltage from 1.25 V to around .8 V which makes it hard for the glo lighter to function (impossible, really). I hate to think of installing a big old knife switch on the top wing of the Staggerwing, but, apparently I'll have to find a better way of switching the current to the lighter than a slide switch. I still haven't tested Jerry's theory, but, I will report back as soon as I do. The 2200 mah cell should work, according to Jerry.

[rick.benjamin]

Use an automotive fuse in place of the switch.

[Ron W3FJW]

Use a pair of Deans plugs with the male Deans shorted. Just pull the male plug out to turn the ckt off. Don't lose it though.