resistor versus regulator

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pcatterall

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I am using a more 'sexy' ( to some)title for this post as non of you boffins answered my last one!!
I am repairing 3 24 volt Eberspacher D1LCs which came in a skip!!
The two older models use a relay and a resistor coil in the glow plug circuit.
The later model has no resister and there is regulator in place of the relay.
The heaters use the same external ECU and internal PCB.
Can anyone explain just what the resistor and regulator do? which is best ( I do note that the resistor gets red hot and could be a fire hazard!!)
Can I buy the regulator 'off the shelf' somewhere; they are about £70 from the dealer.
Alternativly I have several spare resistors so I suppose I could convert the later model heater to the older model by using one of those and a new 'off the shelf' relay.
Thanks for any information on this.
 
Resistors and Regulator

First the regulator .. This will supply a fixed voltage .. Usually written on it .. A common one is a 7805 .. You can put a range of voltages in and will only get 5v out .. So the device is a regulator .. The resistor you have is probably part of a regulator circuit .. It should not be to hot to touch .. This means that there could be a direct short to earth through the resistor .. You can check which component has gone short circuit from a circuit diagram .. If you do not have one I would spend time trying to find one .. You may find that the resistor is part of a transistor circuit and that in the later board this has been replaced by the regulator ..

If you don't know the difference between a regulator and a resistor then you may be in trouble ..

Also bear in mind that resistors come in all sorts of shapes and sizes for a reason and relays have different value coils .. Without an ohm meter to check the circuits you will of course have trouble .. This is probable why they were in the bin .. They are probably EX Heaters
 
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Thanks for the info. I did hear( a rumour) that the 24v D1 used a 12 volt glow plug, I wonder if the resistor controls that.
I can confirm that the resistor does glow red hot and does on every D1LC I have had on test ( about 5), they all worked. I guess that I can test the volts at the glow plug to see what the resistor is doing then look for a regulator to do the same.
 
pcatterall said:
Thanks for the info. I did hear( a rumour) that the 24v D1 used a 12 volt glow plug, I wonder if the resistor controls that.
I can confirm that the resistor does glow red hot and does on every D1LC I have had on test ( about 5), they all worked. I guess that I can test the volts at the glow plug to see what the resistor is doing then look for a regulator to do the same.
Click to expand...

Measure the current as well, the regulator will almost certainly need a heatsink.

A ceramic resistor will get hot, but then they are designed to do that, and probably a simpler modification.

Brian
 
pcatterall said:
I am using a more 'sexy' ( to some)title for this post as non of you boffins answered my last one!!
I am repairing 3 24 volt Eberspacher D1LCs which came in a skip!!
The two older models use a relay and a resistor coil in the glow plug circuit.
The later model has no resister and there is regulator in place of the relay.
The heaters use the same external ECU and internal PCB.
Can anyone explain just what the resistor and regulator do? which is best ( I do note that the resistor gets red hot and could be a fire hazard!!)
Can I buy the regulator 'off the shelf' somewhere; they are about £70 from the dealer.
Alternativly I have several spare resistors so I suppose I could convert the later model heater to the older model by using one of those and a new 'off the shelf' relay.
Thanks for any information on this.
Click to expand...

Perhaps I misunderstand your description, but I'm puzzled because a regulator doesn't do the same job as a relay. If it is simply a regulator, then there must also be some circuitry to switch current to the glowplug.

Whatever this 'regulator' is, it will most certainly be a common device, and available from CPC (for example) at a lower price. What's the part number?
 
pcatterall said:
I am using a more 'sexy' ( to some)title for this post as non of you boffins answered my last one!!
I am repairing 3 24 volt Eberspacher D1LCs which came in a skip!!
The two older models use a relay and a resistor coil in the glow plug circuit.
The later model has no resister and there is regulator in place of the relay.
The heaters use the same external ECU and internal PCB.
Can anyone explain just what the resistor and regulator do? which is best ( I do note that the resistor gets red hot and could be a fire hazard!!)
Can I buy the regulator 'off the shelf' somewhere; they are about £70 from the dealer.
Alternativly I have several spare resistors so I suppose I could convert the later model heater to the older model by using one of those and a new 'off the shelf' relay.
Thanks for any information on this.
Click to expand...

I am not familiar with your model, but the glow plug is there to start the combustion cycle.So the first thing I would do is to check the voltage supplied to the glow plug either using a multi, or reading the numbers of the glow plug itself.
Then check the pin out of the relay and regulator. It might be control +, high current + in, high current + out, and a - line.
In this case it might be that the relay supplies high current + supply on receipt of the control signal from the PCB, and the resistor is to drop the voltage from 24v to 12v (assuming a 12v glow plug)
The regulator would supply a high current 12v + on recipt of the control signal.
I am not clear what exactly you wish to do, but sugguest you either
replace the glow plug with a 24v type and just have the relay, or keep the 12v glowplug and use a resistor and relay - you will need high current versions.
Hope this helps
 
If you don't know the difference between a regulator and a resistor then you may be in trouble ..

Yes, thanks, it is more the practical use of these companants that I was trying to understand. Why did eberspacher change one system for another etc.
 
Perhaps the glow plug is a 12v device and the resistor simply drops the 24v down to 12v for it. the relay is just the switch. This is a quite wasteful (but simple) technique and has a short life span - ie the glowing resistor. The regulator might be a much more clever device which, by switched mode technique, converts 24v to 12v and thus avoids the power wasteage in the series resistor.

Neil
 
Regulators

As Neil says the regulator would best be a switch mode type. This will reduce averall power requirement for the glow plug and reduce the need to dissipate a lot of heat. (plus it can easily switch on and off without a relay)
Using a resistor with a 12v glow plug you must dissipate the same amount of heat in the resistor as the glow plug produces.
A linear regulator (as described by earlier respondants) is effectively an automatic resistor which must still dissipate the same heat. (7812 etc)

A switching regulator is more efficient. Imagine if the 12v glow plug was hit with 24v then turned off before it is destroyed then turned on again at a ratio of 1 to 3 then total power will be the same as using it on 12v full time or using a 24v glow plug. The switching rate can be quite high even to 1000 times per second. You need a capacitor to provide a storage on the supply side so that you are not taking pulses from the battery at that rate but rather from a local storage capacitor. This type of switch mode regulator an be quite simple and the only heating losses are in the transistor itself which will drop about 1 volt at the high current ie 4 times that on 12v. But again the heating is only for 1/4 the time.
If you try to measure the voltage on the glow plug you may get all sorts of results. best is to use an analogue meter with a needle. This will from its own inertia, measure the average voltage. If you try to use a digital voltmeter, this periodically samples the voltage. You might sample at an on or an off period or part of both depending on the rate of switching. Readout could be anything from 0 to 24v. You really need an oscilascope to see what is happening.

note this kind of regulator can be much simpler than a proper switch mode regulator because the glow plug won't mind pulses of 24v but when true12v is required from 24v and produced in a similar manner inductors and more capacitors are needed to get a smooth 12v out. Of course they may have used an off the shelf complete switch mode regulator which does give a smooth 12v but that would be OTT.

You could make your own switcher regulator (power reducer) fairly simply to replace a large glowing resistor. It would essentially have a 555 timer ic driving a large power transistor which switches the current. This could also include electronic current control instead of having a relay. good luck olewill
 
A resistor in line with the glow plug will be acting as a current limiting device (V = I/R) . A linear regulator can be wired to act as a current limiting device. I would be surprised though since even the to55 cases ones are only rated at 3 amps.

So the pertinent questions are.

What is the wattage rating and resistance value of the resistor that gets red hot?

Can you see a part number on the regulator? ( LM 311, 780xx etc )?

Can you measure the voltage across the resistor ( close to 12v gets my bet! )

Does the relay simply turn the supply to the glow plug on and off or does it 'short out' the resistor. ie act as a 2 level circuit for start / run?

BTW the official eber manual lists the part as the 'glow plug regulator' but that may just be German English
 
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William_H said:
As Neil says the regulator would best be a switch mode type. This will reduce averall power requirement for the glow plug and reduce the need to dissipate a lot of heat. (plus it can easily switch on and off without a relay)
Using a resistor with a 12v glow plug you must dissipate the same amount of heat in the resistor as the glow plug produces.
A linear regulator (as described by earlier respondants) is effectively an automatic resistor which must still dissipate the same heat. (7812 etc)

A switching regulator is more efficient. Imagine if the 12v glow plug was hit with 24v then turned off before it is destroyed then turned on again at a ratio of 1 to 3 then total power will be the same as using it on 12v full time or using a 24v glow plug. The switching rate can be quite high even to 1000 times per second. You need a capacitor to provide a storage on the supply side so that you are not taking pulses from the battery at that rate but rather from a local storage capacitor. This type of switch mode regulator an be quite simple and the only heating losses are in the transistor itself which will drop about 1 volt at the high current ie 4 times that on 12v. But again the heating is only for 1/4 the time.
If you try to measure the voltage on the glow plug you may get all sorts of results. best is to use an analogue meter with a needle. This will from its own inertia, measure the average voltage. If you try to use a digital voltmeter, this periodically samples the voltage. You might sample at an on or an off period or part of both depending on the rate of switching. Readout could be anything from 0 to 24v. You really need an oscilascope to see what is happening.

note this kind of regulator can be much simpler than a proper switch mode regulator because the glow plug won't mind pulses of 24v but when true12v is required from 24v and produced in a similar manner inductors and more capacitors are needed to get a smooth 12v out. Of course they may have used an off the shelf complete switch mode regulator which does give a smooth 12v but that would be OTT.

You could make your own switcher regulator (power reducer) fairly simply to replace a large glowing resistor. It would essentially have a 555 timer ic driving a large power transistor which switches the current. This could also include electronic current control instead of having a relay. good luck olewill
Click to expand...
Will
I have a knackered D2 airtronics (ECU gone) Have been thinking of using it in the workshop by putting a manual glow plug switch in circuit, manual switch for the fan BUT need to make a pulsing circuit for the tick tick pump, do you have any very specific ideas on how to create a circuit to do this, perhaps with a rheostat to control the frequency of the "tick" and the speed of the fan?
Stu
 
Does the relay simply turn the supply to the glow plug on and off or does it 'short out' the resistor. ie act as a 2 level circuit for start / run?

I will check the readings as recommended. I do know that the relay ticks when the glow plug and resistor are in use, I did wonder why this was but now assume that it is controlling the power by switching on and off.
Yes the manual calls the device (( on the most modern D1LC, (8113 series I think) a regulator but the diagram looks just like a normal relay))

Thanks for the interest...its all going in and some is sticking!!
 
skipper_stu said:
Will
I have a knackered D2 airtronics (ECU gone) Have been thinking of using it in the workshop by putting a manual glow plug switch in circuit, manual switch for the fan BUT need to make a pulsing circuit for the tick tick pump, do you have any very specific ideas on how to create a circuit to do this, perhaps with a rheostat to control the frequency of the "tick" and the speed of the fan?
Stu
Click to expand...

Look up NE 555 sample circuits. the 555 is perfect for this type of thing. You will need a mosfet or hefty transistor to drive the tick tock pump ( some 555 ciscuits will have a relay driver option ) Put a flyback diode across the pump coil drive to stop the circuit self destructing through back emf. I would also look at sensing the flame detector device as well. if the fire goes out you dont want to keep pumping diesel into the chamber.

Actually any chance someone has a blown ECU they want to dump my way. I may be able to look at repairing them. I have just looked at replacement prices!
 
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nimbusgb said:
Look up NE 555 sample circuits. the 555 is perfect for this type of thing. You will need a mosfet or hefty transistor to drive the tick tock pump ( some 555 ciscuits will have a relay driver option ) Put a flyback diode across the pump coil drive to stop the circuit self destructing through back emf. I would also look at sensing the flame detector device as well. if the fire goes out you dont want to keep pumping diesel into the chamber.

Actually any chance someone has a blown ECU they want to dump my way. I may be able to look at repairing them. I have just looked at replacement prices!
Click to expand...
Thanks for the pointer, have loads of mosfets from old computer power supplies. will do some more research now i know where to go, i presume the diode on the drive is just to stop flow back?
stu
 
nimbusgb said:
Look up NE 555 sample circuits. the 555 is perfect for this type of thing. You will need a mosfet or hefty transistor to drive the tick tock pump ( some 555 ciscuits will have a relay driver option ) Put a flyback diode across the pump coil drive to stop the circuit self destructing through back emf. I would also look at sensing the flame detector device as well. if the fire goes out you dont want to keep pumping diesel into the chamber.

Actually any chance someone has a blown ECU they want to dump my way. I may be able to look at repairing them. I have just looked at replacement prices!
Click to expand...
Will post a pic of the one i have taken apart on monday, prob is that they assemble sub components and then glue them all together, just to get it apart destroys the input and output connections for a start.
Stu
 
nimbusgb said:
ahhhhh. I thought as much but it couldn't be too difficult to produce a replacement that does the same job ......
Click to expand...
when i post the pics tomorrow you can see that we could clean out the old pcb and there should be room to do something. Basically it needs a mosfet and timer to control the tick tick pump, somehow need to control the speed of that with the speed of the fan and then a safety circuit that takes in to account overheat and flame failure (basically they are 2 resistances that change resistance as heat increases, http://www.espar.com/documents/airtronic.pdf is where the handbook is that gives the values at different temps) The internal thermo stat doesnt really matter, the majority of D2s run at full chat anyway.
Stu
 
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