This follows on from "hiperterminal responce" but as I have moved on I have started another thread.
Coming back to my still unsolved problems I am faced with another.U3 is getting to hot to touch after only a 20 or 30 seconds powered up. The oscilator is also warm and the 5v feed has droped to 2v. Could a fault with the oscilator pull the voltage down this much?
I also have found when looking for shorts on the PCB that part of the track that links R3 to R2 is missing.This looks to be part of a driver feeding Q1 which I dont think I am using so this is also puzzling me.
Any advice would be great.
Ps don't suppose the oscilator could have caused my other problems?
U3 geting hot.
Moderators: JeffC, rdoherty, stieg, brentp
U3 shouldn't run above
U3 shouldn't run above ambient, except if you happen to be constantly driving LEDs or relays, so you definitely have a problem 
The oscillator should never run warm at all.
If you are absolutely sure that you don't have any short circuits (and real short circuits would see the 5v feed at 0v anyway) then you maybe have got a component failure somewhere - and if the oscillator is the only warm thing apart from U3, that would be the first thing to unsolder to see if that's causing the problem.
...and assuming you have a V2 board, given the way you are describing components...
Where has the track between R3 and R2 gone missing to? It's a very crucial link and two things come from your comments:
1. you definitely are using Q1 - it's how the incoming PIP signal from the EDIS module get's into the unit!
2. R3 and R2 aren't a driver for Q1 - in simple terms they act as a potential divider that cuts down the (almost) +12v PIP signal from the emitter of Q1 to just under 5v to act as the input to the processor IRQ1 pin. If the break:
- is effectively immediately to the right of the wiggly line for R2, then you won't be getting any PIP signal into the processor
- is effectively immediately above the wiggly line for R3, then you are losing the potential divider effect of R3. However D1 will be acting as a clamp diode, ensuring that the voltage on the IRQ1 pin doesn't exceed 5.1v and hence damaging the processor - a neat piece of circuit design! However, I'm not sure the IRQ1 input will work as required as I don't see how the IRQ line gets pulled low without R3 in place....
...but the bottom line is that you DO need R3 and R2 connected!
The oscillator should never run warm at all.
If you are absolutely sure that you don't have any short circuits (and real short circuits would see the 5v feed at 0v anyway) then you maybe have got a component failure somewhere - and if the oscillator is the only warm thing apart from U3, that would be the first thing to unsolder to see if that's causing the problem.
...and assuming you have a V2 board, given the way you are describing components...
Where has the track between R3 and R2 gone missing to? It's a very crucial link and two things come from your comments:
1. you definitely are using Q1 - it's how the incoming PIP signal from the EDIS module get's into the unit!
2. R3 and R2 aren't a driver for Q1 - in simple terms they act as a potential divider that cuts down the (almost) +12v PIP signal from the emitter of Q1 to just under 5v to act as the input to the processor IRQ1 pin. If the break:
- is effectively immediately to the right of the wiggly line for R2, then you won't be getting any PIP signal into the processor
- is effectively immediately above the wiggly line for R3, then you are losing the potential divider effect of R3. However D1 will be acting as a clamp diode, ensuring that the voltage on the IRQ1 pin doesn't exceed 5.1v and hence damaging the processor - a neat piece of circuit design! However, I'm not sure the IRQ1 input will work as required as I don't see how the IRQ line gets pulled low without R3 in place....
...but the bottom line is that you DO need R3 and R2 connected!
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
Removed the oscilator
Hi Martin thanks for your help again.
Removed the oscilator, processor and the max232 chip and I still have the problem.
As for the missing track haveing another look it's the track that links R1 to R10 on the outside of the board (V2) and not R2/R3 as I first thaught. Is it posable that what ever caused the problem sent to much current along this track making it act like a fuse?
Removed the oscilator, processor and the max232 chip and I still have the problem.
As for the missing track haveing another look it's the track that links R1 to R10 on the outside of the board (V2) and not R2/R3 as I first thaught. Is it posable that what ever caused the problem sent to much current along this track making it act like a fuse?
Hmmmm...well if the track
Hmmmm...well if the track that is broken is the main run BETWEEN R1 and R10 (rather than on the small 90 deg right turn just before R10) then the SAW signal won't be getting to the Molex and you need to fix that in due course
It sounds like you've had a short circuit somewhere/sometime and the track has, indeed, acted like a fuse and just blown away - as I write this I'm looking at a V2 board that has had just that problem sometime in the past (in another area). There's a wire link replacing it and it works just fine.
I think there's two choices:
1. you've got a complete or almost complete short somewhere and you'll have to keep taking stuff out until the regulator runs cold and you've got +5v on the main supply
2. the problem is the regulator itself, maybe due to a previous short circuit. Take it out and see what the resistance is between the +5v track and the earth track - with the main components out of the board it should be pretty high. To be honest, any old 7805 regulator will do, and you could get a replacement at Maplins (assuming you're in the UK) cheaply.
Good luck...report back
It sounds like you've had a short circuit somewhere/sometime and the track has, indeed, acted like a fuse and just blown away - as I write this I'm looking at a V2 board that has had just that problem sometime in the past (in another area). There's a wire link replacing it and it works just fine.
I think there's two choices:
1. you've got a complete or almost complete short somewhere and you'll have to keep taking stuff out until the regulator runs cold and you've got +5v on the main supply
2. the problem is the regulator itself, maybe due to a previous short circuit. Take it out and see what the resistance is between the +5v track and the earth track - with the main components out of the board it should be pretty high. To be honest, any old 7805 regulator will do, and you could get a replacement at Maplins (assuming you're in the UK) cheaply.
Good luck...report back
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
12 Ohms
I've got a 12 Ohms load on the 5v side with all the components instaled bar U3.
first removed J1 then C2,D3,C7 but the only time the resistance went up was when the processor was removed it is now 35 Ohms.
So as I look at it now the only things left conected now J1 is out are ocsilator and the RS232 socket so am puzzeled as U3 was still getting hot when oscilator was removed.
first removed J1 then C2,D3,C7 but the only time the resistance went up was when the processor was removed it is now 35 Ohms.
So as I look at it now the only things left conected now J1 is out are ocsilator and the RS232 socket so am puzzeled as U3 was still getting hot when oscilator was removed.
Hmmm..I'm running out of
Hmmm..I'm running out of ideas
35 ohms, if correct, is still far too high - this will draw about 140ma which is far, far too much.
Just gotta keep taking out stuff I'm afraid,
This might make a bit of a mess of the board, but I can't really work out what to suggest otherwise.
Could be an opprtunity to upgrade to a V3 board? - a lot of the major components are common and it's generally regarded as a good improvement
35 ohms, if correct, is still far too high - this will draw about 140ma which is far, far too much.
Just gotta keep taking out stuff I'm afraid,
This might make a bit of a mess of the board, but I can't really work out what to suggest otherwise.
Could be an opprtunity to upgrade to a V3 board? - a lot of the major components are common and it's generally regarded as a good improvement
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
Think I have found the
Think I have found the problem. The processor has a load of 18 ohms across the 5V and ground and the ossilator 35 ohms. Previously I had been removing the components one at a time and then checking U3 for heat not thinking the problem may have been with more than one. The load on U3 with these two removed is now 1.3K.
Am I on the right track and where is the best place to get replacments (I am in the UK)?
Thanks.
Am I on the right track and where is the best place to get replacments (I am in the UK)?
Thanks.
Send me an email
Send me an email (moc.liamtoh@srenellim - it's backwards!) and I can point you in the right direction....
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
I now have ignition advance,
I now have ignition advance, but am still a little worried about the running temprature of U3. I have a load of 1k conected to the loom and 1.3k disconected. Is this OK? or is it possable U3 has been has been damaged?
Weird problem.
The only thing that U3 (Voltage regulator) is running is the MJLJ itself. Since the transistors on the user defined outputs switch ground, this current is not routed through U3.
How are you measuring load on the loom? Usually I measure current consumption by putting an ammeter inline with the power supply.
How much current does it consume when you have the processor removed?
Another possibility is that a component may have become damaged during the original problem and/or debug proocess.
How are you measuring load on the loom? Usually I measure current consumption by putting an ammeter inline with the power supply.
How much current does it consume when you have the processor removed?
Another possibility is that a component may have become damaged during the original problem and/or debug proocess.
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
By load I mean the
By load I mean the resistance between +5V and ground with U3 removed. I was unsure if there was a 5V supply to the edis unit so took the readings on the bench and again pluged into the car.
So 5V and a load of 1300 ohms is .00384 Amps. Is this enough current draw on U3 for it to get hot when running or have I a problem?
So 5V and a load of 1300 ohms is .00384 Amps. Is this enough current draw on U3 for it to get hot when running or have I a problem?
Agreed, that shouldn't cause
Agreed, that shouldn't cause U3 to heat up. but you've measured a static load, not a dynamic one as the circuit is running.
Try putting an ammeter in series with the 12v power supply to the MJLJ and see how much the current draw is. You could start off with all components installed.
I've never measured the current draw to be honest, so I'll do that today or tonight. Since the Vreg only powers the MJLJ itself, and no other external circuits, except for the +5v reference for the TPS, the current draw should be negligible.
Brent
Try putting an ammeter in series with the 12v power supply to the MJLJ and see how much the current draw is. You could start off with all components installed.
I've never measured the current draw to be honest, so I'll do that today or tonight. Since the Vreg only powers the MJLJ itself, and no other external circuits, except for the +5v reference for the TPS, the current draw should be negligible.
Brent
**beware - back of envelope
**beware - back of envelope calculations ahead**
On one of my V3 boards with a MAP sensor the current drawn, on the bench, not connected to any EDIS components, with a 9v battery are:
- 28mA with all components fitted
- 24mA with the MAX232 removed
- 24mA with the MAX232 and ULN2003 removed
- 12mA with the MAX232, ULN2003 and processor removed
So the regulator power dissipation is 4 * 28 mW, say 100mW. Or with a 12v supply, say 200mW worst case. For a typical TO-220 cased regulator, the thermal resistance is 50 degrees C/Watt from case to ambient, so it should be rising about 5 (or 10) degrees above ambient.
The regulator is attached to the board by a M3 nut and bolt, which increases the thermal efficiency a little.
(EDIT) With the 9v battery attached for a long time, I can feel a very minor temperature rise (2-3 degrees?) on the regulator - which is nice as it just about fits the maths. Don't have a thermometer! (/EDIT)
Working backwards, let's say you are feeling 30 degrees above ambient with a 12V supply. So the regulator is dissipating 0.6W, which means its passing in the order of 85mA - getting towards 4 times what it should be.
Report back on the current drawn with different components removed....
On one of my V3 boards with a MAP sensor the current drawn, on the bench, not connected to any EDIS components, with a 9v battery are:
- 28mA with all components fitted
- 24mA with the MAX232 removed
- 24mA with the MAX232 and ULN2003 removed
- 12mA with the MAX232, ULN2003 and processor removed
So the regulator power dissipation is 4 * 28 mW, say 100mW. Or with a 12v supply, say 200mW worst case. For a typical TO-220 cased regulator, the thermal resistance is 50 degrees C/Watt from case to ambient, so it should be rising about 5 (or 10) degrees above ambient.
The regulator is attached to the board by a M3 nut and bolt, which increases the thermal efficiency a little.
(EDIT) With the 9v battery attached for a long time, I can feel a very minor temperature rise (2-3 degrees?) on the regulator - which is nice as it just about fits the maths. Don't have a thermometer! (/EDIT)
Working backwards, let's say you are feeling 30 degrees above ambient with a 12V supply. So the regulator is dissipating 0.6W, which means its passing in the order of 85mA - getting towards 4 times what it should be.
Report back on the current drawn with different components removed....
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russell_west
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- Joined: Mon Mar 01, 2004 3:20 pm
One step forward two back.
One step forward two back. Had the mjlt running on the car checking with a digital thermomiter the temprature rise and useing the lap top to see if there was a responce to changes in advance. All was well untill I just lost coms and the thing just runs at fixed advance. Is there any one I can pay to look at it for me, I just seem to be going around in circles and time is not on my side? The temprature of U3 rose from 25C to 40C when running.