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Old May 14, 2011, 01:41 PM
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One Cell Lipo powered glow driver

Just want to share my recent project ...



The FET got very hot , can't be used for long period .



This one is better

Note :
Fuse is to protect the circuit , not the glow plug



I got the FET from ex BL esc ....
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Old May 14, 2011, 02:51 PM
"Simplify, then add lightness"
Raleigh,NC
Joined Nov 2000
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I have seen several people trying to use linear regulators to power glow plugs which is a real waste of heat and power. Good to have a thread to point them to.

I understand that you were building from parts you had, but two comments for people buying parts to build one. First, the NE555 is specified for operation from 4.5V to 16V so is being operated outside it specifications. There are CMOS versions of 555 that are rated for lower voltages and if buying new parts they would be a much better choice. In the US, you can get the TLC555 at Radio Shack and it is rated for operation from 2 to 15v. The 4435 is also extremely marginal on a single lipo which is why you need two of them. If buying parts, a much better choice would be an IRF7420 and one of them should work fine.
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Old May 14, 2011, 11:00 PM
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Jeff ,thanks for your input .
NE555 can be powered with 3 volt although the datasheet says "min 4.5 volt" .
CMOS 7755 , TCL555 should be better .
IRF7420 to replace two 4355 is a good choice .

Since I live in a rural district , it is hard to find those components in local shop ; so I use my old 'stock component'

I will redraw this circuit with better components as you suggested .
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Last edited by Wind Raider; May 14, 2011 at 11:38 PM.
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Old May 15, 2011, 12:06 AM
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I haven't tested this circuit . But it should work fine .
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Last edited by Wind Raider; May 15, 2011 at 12:44 AM.
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Old May 15, 2011, 12:16 AM
just look at it smokin'
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Quote:
Originally Posted by jeffs555 View Post
I have seen several people trying to use linear regulators to power glow plugs which is a real waste of heat and power. Good to have a thread to point them to.

I understand that you were building from parts you had, but two comments for people buying parts to build one. First, the NE555 is specified for operation from 4.5V to 16V so is being operated outside it specifications. There are CMOS versions of 555 that are rated for lower voltages and if buying new parts they would be a much better choice. In the US, you can get the TLC555 at Radio Shack and it is rated for operation from 2 to 15v. The 4435 is also extremely marginal on a single lipo which is why you need two of them. If buying parts, a much better choice would be an IRF7420 and one of them should work fine.
that's not a linear regulator, it just gives out the short circuit to the li-po using the heating element with a repetition rate.
Peak currents are probably very high with high Đi/Đt that may cause radio interference.
Sure, it works, as long as your li-po can take the high peac currents, and your fet does not go sc.
You may prefer adding sqrt(-1) to the system for better performance, though it will be a few gramms heavier.

Btw.: you can use the switch to switch and 1m mosfet control instead of the full circuit current...

Z
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Old May 15, 2011, 12:38 AM
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@z-matrix : yup , that's non linier regulator .


testing version1
One 900 mAh Lipo can be used for 15 minutes continous ON . The battery is just warm a bit not hot .

Two Fets has advantages :
1. lowered the ON resistance , so we can 'dig' more mAH form the battery
2. the fet will be cooler .

btw , can you explain more about sqrt(-1) ?
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Last edited by Wind Raider; May 15, 2011 at 10:35 AM.
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Old May 15, 2011, 01:06 AM
just look at it smokin'
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Quote:
Originally Posted by Wind Raider View Post
btw , can you explain more about sqrt(-1) ?
its the square root of -1
was recommending the use of an inductor and capacitor to smooth the peak current.
A Buck regulator looks like this for example: http://en.wikipedia.org/wiki/Buck_converter

Z
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Old May 15, 2011, 04:42 AM
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The 555 is configured in astable oscillator .
Fet is used as electronic switch and also 'invert' 555 output .
Fet will be ON if output of 555 (pin3 ) is OFF ('low') .
The duty cycle ( to glowplug) is varied from 33,5 % to 1 %(adjustable)

The glow plug can take lipo output voltage in very short periods approx 1 ms.
The output to glowplug is approx 3.7 volt ( lipo nominal voltage )
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Old May 15, 2011, 09:28 AM
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did to try with some of 3pins Mosfet?




Thank..
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Old May 15, 2011, 10:11 AM
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The gate voltage threshold of common 3 pins FET is too high ; not suitable for this circuit ( with 1 cell lipo ) .
I didn't know whether 3 pins Fet with low voltage threshold available or not .
Perhaps Jeff can suggest that .
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Old May 15, 2011, 02:53 PM
"Simplify, then add lightness"
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Wind Raider is right. Most of the mosfets rated for Vgs of less than 4.5V are in SO-8 or smaller packages. Here is one in TO-220 that is rated down to 2.5V, but it has a rather high on resistance of 0.07 ohms. Two of them would work ok, or you could use just one with a small heat sink.

http://mouser.com/search/ProductDeta...opOw%3d%3d&amp
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Old May 15, 2011, 09:32 PM
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I currently use a C cell rechargebable battery, a 10amp micro switch and alligator clips for onboard glow. Works great.
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Old May 15, 2011, 11:53 PM
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@disarray : yup , quick and easy method .
You use it as onboard glow driver ?
At what percentage of WOT ( wide open throttle ) you set the switch on/off ?
Alligator can be loose sometimes , you 'd better use glowplug cap instead .
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Old May 16, 2011, 08:18 AM
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Originally Posted by Wind Raider View Post
@disarray : yup , quick and easy method .
You use it as onboard glow driver ?
At what percentage of WOT ( wide open throttle ) you set the switch on/off ?
Alligator can be loose sometimes , you 'd better use glowplug cap instead .
It is on all the time. On this plane, I have 4 engines, so I use one toggle switch and one C cell for each glow plug. I like the clips, because I can easily take them loose to charge the batteries. I have never had a cell go dead, but I usually only fly this plane for about 30 minutes to an hour on a weekend.
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Old May 24, 2011, 02:11 AM
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Here is the version 3
with 20 seconds timer to control the glow heater

One Cell Lipo powered Glow Igniter version 3 (2 min 19 sec)
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