Glow plug light idea

[bhtooefr]

Hooking up some form of light to the glow plug circuit, so that it lights up whenever the GPs are on is a very common thing to do.

I had a better idea.

Note that on the CE1 cars, there's a row of lights that's unused underneath the five indicator lights.

I'm considering this:

Take a PIC, or other microcontroller (such as a BASIC Stamp). Program it such that it can read the amperage draw from the GP circuit. Wire it into five LEDs.

When the PIC is reading a 48A draw, the first four will be lit.

Anything deviating from that will cause the fifth LED to be lit - that'll be the GP fault LED.

If it's 36A, the first three and last one will be lit.

24A means that the first two and last one will be lit.

12A means, of course, that the first and last will be lit.

And, 0A means that only the fifth will be lit.

How does this idea sound, adding a complete GP monitoring circuit that tells you how many GPs are working into the cluster?

[steve]

great idea!!!  

make the 5th LED a different color than the first 4.

Sounds cool, but my electrical knowledge stops just past knowing to not let the smoke out...

[bhtooefr]

Ahh... just read back through my post.

There'd still be power supplied to the GPs, just not any draw if they're all dead, so something driven off of the GP line would be powered, right?

If not, I'd have to take a different input to only have it throw an error when the GPs are actually turned on.

Edit: And, yes, I would use green LEDs for the first four, and red for the last one.

[MacGyver]

There'd still be power supplied to the GPs, just not any draw if they're all dead, so something driven off of the GP line would be powered, right?

Yep, and if the lights don't come on, that tells you your fuse is blown...or your relay.

How are you gonna read current? I can get my hands on a decent quantity of fairly small 50A and 100A shunts, with standard 50mv output.
Sent a couple to a guy in Calgary that wanted to put one in his GP line so he could check for failures quickly with a meter, without removing anything. Never heard back how he made out.

Maybe you could make a 4-wire harness like QuickTD has, monitor each line, and use bi-colour LED's to show that each GP is ok...?

I put a light inline with the GP's in an old Tempo diesel I had, was a nice reasurrance they were working after having had trouble with it. The Tempo had reduced voltage afterglow, and the bulb dimmed to show this too of course.

[LeeG]

Someone suggested ditching the bus bar and rewiring the plugs so that there is a wire to each of them to make it easier to find the dead one next time around.  I am going to do that next time I have to take bus bar off.  If you did this you could measure the draw for each plug and only light its LED if it was working.  

I've been playing around with another way to find a dead plug:  I've got one of those instant reading digital  infrared thermometers.  You cant acuratly take a reading past all the lines and hoses, but if you make a  paper tube 1/2" diameter or so and stuff it down through the hoses, it seems like you can get repeatable readings off the plug where it enters head.  After cycling the plugs 3 times there was a 5c temp rise when I tested this.  I need to do this again using 4 tubes, I'll pass the results along if it looks good.  I got the IR thermo from PA for something like $80C.

[bhtooefr]

Eek!

While a version with each of the first four LEDs being connected to a single GP, and a light tied to a (lower end in this case) PIC going off whenever it drops below 48A isn't too excessive, THAT is, libbybapa

However, my version is simpler wiring, even if it's harder to program But, programming only has to happen once. Wiring has to happen with each install, if someone wanted to do this.

[Mathdiesel]

Another possibility would be to read voltage across the glow plug rather than current. A dead glow plug will have 0V across it since its an open-circuit. I know there is a bit more wiring involved, but you would know which glow plug is dead rather rather than knowing that "one" is burnt.

This is the way that i see it, i'm sure it could be made with a PIC, though i'm getting in a project like this, i got enough with my owns  :wink:

[chrissev]

Hooking up some form of light to the glow plug circuit, so that it lights up whenever the GPs are on is a very common thing to do.

I had a better idea.

Note that on the CE1 cars, there's a row of lights that's unused underneath the five indicator lights.

those aren't lights.  they're just little black plastic bubbles.  Nothing behind them.  You'd have to take them out and replace them with LEDs.  From what I remember of the PC board that is in there, you'd need to make some new holes and run some new etching on the back of it.

[QuickTD]

A really slick and simple method of monitoring glow plug function is used in the bosch glow plug controllers of BMW and mercedes diesels. Each glow plug is fed via an individual wire from the controller. Inside the controller each of the individual wires leaving the main switched "bus" is coiled tightly around a reed switch. All of this is compactly mounted on the circuit board. A reed switch is a small glass tube containing a set of contacts, The core material of these contacts is iron, in the presence of a magnetic field these contacts also magnetise and close. The wire coils feeding each glow plug provide the magnetic field to actuate the reed switch. If the glow plug is burned out, no current travels through it, no magnetic field is generated and the reed switch remains open. The bosch controller uses the input from these relays to reduce the glow time if one or more glow plugs are burned out. This prevents the other (fast glow) plugs from burning out due to excessive voltage.

 This idea could be used to build a simple glow plug monitoring circuit. All that is required would be 4 reed switches 4 small coils of 14 guage wire and 4 indicators (LED's would be good). Wire up a harness (like mine) with 4 seperate wires feeding the glow plugs via the small coils around the reed switches and connect the reed switches to the indicators. Turn the key, if all 4 light you're good to go if any are out it would be a simple matter to find and replace them.

[bhtooefr]

chrissev: I figured that they were something like that - I don't think it'd be too hard to fix that, though.

QuickTD: While not as, umm, technically fun as my idea, it's VERY interesting, and more useful. Also, the fun could be extended to CE2 cars, as that could be done with only four LEDs (although my idea would also work with four - this would be harder to make work with five).

[LeeG]

QuickTD:  is that BMW / Merc controller something that could be easily hacked?  Or can someone point us to a source for suitable reed switches?
Is 14 gauge wire heavy enough to feed a glowplug?

I can see a marketable product here.  A wiring harness that incorporates glowplug status lights and is a bolt in replacement for bus bar.  4, 6 and 8 cylinder verisons, optional plug in extension to provide addional LEDs on the dash.  Make millions  :shock:  send me royalties   !

[bhtooefr]

In fact, one could overhaul clusters (you know, fix odometers, replace LEDs, etc.), and offer an option so as to be compatible with such a system.

[QuickTD]

QuickTD: is that BMW / Merc controller something that could be easily hacked? Or can someone point us to a source for suitable reed switches?
Is 14 gauge wire heavy enough to feed a glowplug?

Suitable reed switches are generally available, try your local electronics hobbiest store, or any of the big online suppliers, digi-key, newark etc. 14 guage solid wire can handle 15 amps continuous, more in short doses. Plenty adequate for a single glow plug. In the merc/BMW controllers the coil is uninsulated wire and is placed around the reed switch prior to the whole assembly being soldered to the circuit board. If there was demand, construction of such a device is well inside my realm of expertise...

[ricosuave]

There'd still be power supplied to the GPs, just not any draw if they're all dead, so something driven off of the GP line would be powered, right?

Yep, and if the lights don't come on, that tells you your fuse is blown...or your relay.

How are you gonna read current? I can get my hands on a decent quantity of fairly small 50A and 100A shunts, with standard 50mv output.
Sent a couple to a guy in Calgary that wanted to put one in his GP line so he could check for failures quickly with a meter, without removing anything. Never heard back how he made out.

Maybe you could make a 4-wire harness like QuickTD has, monitor each line, and use bi-colour LED's to show that each GP is ok...?

I put a light inline with the GP's in an old Tempo diesel I had, was a nice reasurrance they were working after having had trouble with it. The Tempo had reduced voltage afterglow, and the bulb dimmed to show this too of course.

That was me LOL

Have had no need to install them as of yet...

It's on the to do list for this year...

[Mark(The Miser)UK]

:idea: This is something I designed last year (January) Totally contemporary with Rabbits/Quantae  Reliably has no moving parts or micro electronics beyond the diodes and LEDs LEDs light after glowplugs extinguish.  Failure of glowplug and LED goes out.
 Failure of 50A fuse and LEDs stay on when starting car (trying to start )
The voltage drop may extend life of glowplugs for those who insist on running 'high' voltages out of their alternators :idea:

Use one of the blank switch covers.
 Supplement with a big LED in middle of switch for direct link to fuse as additional bling... :shock:  
Add Hasselhoff effects if you wish... :twisted: