[Rich]

Originally Posted by RavenTai

...It is harder to accurately measure needle movement than temperature and voltage...

Create a paper template with a radial graph. Tape to gauge behind the needle. Video tape the gauge and temp readout simultaneously while under test.

BTW, use cooking oil to avoid the nasty smell. Toss in some taters if you get hungry.

[landtank]

This stuff looks great. It's funny how sensitive the oil pressure guage seems and the temp just flat lines. I'm with Semlin here as far as what how I'd like my guage to work. That is near centered when normal and red lined at AC cut out. That way I could turn off the AC if I started to climb near that point ahead of time.

As far as the viewing angle, it will all be different for all of us and just something we will need to adjust to after the change.

Nice work!!!

[RavenTai]

Semlin, I have been reading the gauge by trying to square off on the needle base. It has vertical sides to sight down; I think that will have to be our datum line for viewing angle and each driver can adjust from there. I am hoping to set up the test bed so the gauge can stay stationary (as it sits now I need access to the back side to take measurements) and take photos from a tripod with the DMM and digital thermometer in view, that should solve viewing angle and provide angle measurements, also the voltage/angle/temperature readings will be taken at the exact same moment instead of a slight delay when done by hand

After I am done with everything I will look into taking the gauge apart to see how hard it would be to apply an overlay. Don’t want to do that until I have all testing complete.

I can come up with different ranges but I am only going to test one in my truck, if you chosse one of the others you will be the guinea pig for that setting.

Had some time today and did a second cook, this time the diode was bypassed using the ammeter of my DMM, this is not ideal as an ammeter has some resistance but I am hesitant to modify the gauge until I get the test bed right and get a all the info I can out f the gauge as it sits stock. I have some ideas and parts on order to this end.

Making a Wheatstone bridge using the gauge winding the way Toyota did has a side effect, it is source voltage sensitive, and a true whetstone bridge is not. Higher source voltage makes the range slightly wider, the center points stays the same though.

I found my battery charger but did not have enough time to get the voltage up to 14.x where it should be for accurate testing but here are some early rough returns, source voltage was increasing the entire time so these #’s will not be repeatable.

Pegged “C” 180
Cold line 190
Center 210-215 (DMM was busy so had find get center by eye)
Bottom of red 240
Top of red 247
Pegged on the “H” 255

I don’t think that will quite work for anybody but it would be simple to do just solder in one wire. If I were to shift that whole scale down about 13 degrees I would be happy with that. It would be simple, one resistor and one wire to solder in.

The total sweep of the needle is just under 90 degrees (angle degrees) and 75 temperature degrees, this is almost the maximum resolution, and it can only go down from here.

One other thing that is bugging me is what makes the needle peg to C when the power is removed? There has to be a small spring or magnet in the air core motor somewhere.

I will have most of a day Tuesday to work on this and should make good progress.

Rich I should have used cooking oil, I though about it but all I had around was extra virgin olive oil to expensive to fill a pot with. I should have bought some cheap veggie oil.

Originally Posted by landtank

This stuff looks great. It's funny how sensitive the oil pressure guage seems and the temp just flat lines. I'm with Semlin here as far as what how I'd like my guage to work. That is near centered when normal and red lined at AC cut out. That way I could turn off the AC if I started to climb near that point ahead of time.

As far as the viewing angle, it will all be different for all of us and just something we will need to adjust to after the change.

Nice work!!!

The Miata guy did something interesting, he gave values for test resistors that temporarily replace the thermistor to test the modified gauge, maybe we can do the same, this will test the mod and also give you an opportunity to see the angles at simulated temperatures.

[semlin]

raventai

a 13 degree drop instigated by a single resister sounds good to me too. I guess we need to see how it works at 14 volts but if it's close... I'm there.

one question, and pardon my ignorance asking it as my understanding of electricity is at the level of ben franklin before the kite, so bear with me. you mentioned that the centre or dead point involves no voltage, and you mentioned the resister heats up when reading higher temps because of voltage. you may be talking about different things, but if the gauge is seeing 0v at centre and voltage at other temps, we should be sure all the components can take voltage on a sustained basis without hearing if we use a fully responsive gauge because it is unlikely the gauge will ever be centred for long. I am sure you have thought of this, but just thought I'd mention it because the alternative seems to me to introduce a different diode with say a circa 190-205 dead spot. anyway no need for a detailed explanation if you've got this covered. it's more a comment, as I lost your technical explanataion a while back before we crossed the whetstone bridge .

[RavenTai]

From this thread

http://forum.ih8mud.com/80-series-tech/59453-what-your-system-voltage.html

So far seams like 14.5 is a common voltage so I will try to shoot for that. (Mine was 14.47 I rounded up)


Semlin

Simple answer: talking about two different parts of the circuit. the coil L1 drops 0 volts and passes 0 amps at center, the resistor R1 (75 ohm resistor) drops varying levels voltage and passes of varying levels current at all temperatures.

After mod currents (amperage) will be the same and in some areas less than as stock for a given temperature so we will be safe. Also the 75 ohm resistor (only under built part in this circuit) will be upgraded form stock to better handle the load.

I don’t think this is above anybody here, you all are smart folks in one field or another. It is just that if you have never looked into this stuff it sounds like Greek. I would be glad to try to give a layman’s explanation if you want.


the folowing is probably the best of the schematics to look at for understanding, all of them are electrically the same just diffrent arrangment of the parts for clarity of certian points.

[RavenTai]

For Semlin

[semlin]

?? i'm hoping there is a PM to go with that or maybe it will make sense when i get there. I'll try to pick it up saturday one way or another.

[RavenTai]

"i'm hoping there is a PM to go with that"


There is, just sent sorry for the timing

[semlin]

ok raventai I have an official 93 factory temp gauge. unfortunately my digital camera is horrible at close ups. I think you can see enough to ask questions.

in the mean time I'll se about shipping it off to you...

[semlin]

using your 1997 gauge photo (attached) as a reference the back panel in virtually identical.. difference are

1. pn# at top is 769902-961 on mine, looks like 769916-920 on yours

2. third kanji script down, the box on the left looks like it has an H or M in the middle where you have two straight vertical lines. otherwise all the exact same script.

3.at the bottom where you have an "IGN" labelled bass nut, I have one of my 4 raised mounting points still labelled "ign". Where you have the post just below, I have nothing and the circuit board copper does not branch out.

4 the two upper mounting posts on mine have round brass bushings unlike the other two posts which have the same hexagonal style as yours.

[semlin]

comparing to your side view from the 1997 the only difference is in the colouring of the resister. mine is light blue with gold/black/green/purple stripes. the diode has a black stipe, a black circle and a lighter stripe.

[RavenTai]

Originally Posted by semlin

comparing to your side view from the 1997 the only difference is in the colouring of the resister. mine is light blue with gold/black/green/purple stripes. the diode has a black stipe, a black circle and a lighter stripe.

Man you are ahead of me, I was typing up some of those differences and was about to ask for clarification of the resistor colors

It is 75 Ohms just like the 97, but it looks much beefier and probably better at dissipating the heat, on the 97 it is actually written out instead of using the resistor color code.

http://www.electrician.com/resist_calc/resist_calc.htm

So far it looks to be electrically the same and that post movement could be the only reason it got a different part #, the 97 gauge will not bolt up in a 93 cluster and vise versa, it is odd both the 97 and 93 have all the same drilled holes, did they predict the future?


I assume the yellow marks are from the yard? Was it expensive?

[semlin]

C$50 which I figure is cheap if I get a responsive gauge out of it. the yard guy made the marks so I could not try and return it...

I drove 600 miles this weekend to visit a friend and drove over the coquihalla, a major mountain pass pushing the motor hard all the way up. I was running over 3000rpm on a sustained basis with portions over 40000 for about 10km and climbing steadily for 30 km and the gauge never budged.

[RavenTai]

Cool let me know if you need anything,

made some progress last Tuesday, did a full temp thermistor cook and then a needle position vs temp vs voltage across L1 coil cook, I made a animated gif the cook from 135F to 272F but it is 5.3MB and I am having a hard time getting it posted as it is to large to be attached and I don’t have hosting anymore.

Need to do a few small things and will be ready to order resistors and mod the gauge and test the mod. Should get that done this Tuesday.

[loquito]

[RavenTai]

somebody down load this (right click, save target as, should be 5.13MB) and then open it in internet explorer and tell me it is it all garbled. and if it goes all the way to 272*F


Animated Gif

[Rich]

Worked ok for me when I saved and then opened with IE from window explorer. Plays back a bit fast. Good job.

However, if, after the download, I select the open button from the download dialog, then it stopped after showing only a portion of the frames.

[RavenTai]

Thanks Rich


I also get that to with "open", I assume you have windows XP? stock "open" for a .gif under XP is windows picture and fax viewer, for some reason it only plays half of it, I don’t know why, that is my first animated gif so I am not to keen on the particulars, I do know the standard did not have files this large in mind. For some reason when I try to DL from that sources it gets all screwy, Probably has somethign to with it coming from and going to the same place. Firefox refuses to open it at all even locally in explorer.

That may be available all of tonight, after that availability will be spotty and it may fail at any moment as my IP is now dynamic :( I really miss my static IP and Fedora/Apache server.


this is the stock response of the gauge with all stock parts, The frames are purposely not spaced equally, that is about half of the pics I took and did not plan on making that “vid” wile taking the pics so wound up with unevenly spaced frames as far as temperature, so I adjusted the timing of each frame to make for 10 degrees per second, thought on the fast speed was to show needle sweep rate but people would probably also be interested in one slow enough to correlate temps to needle position. when I get some time I will adjust that.

The volt meter is showing volt drop across L1 inductor, wile voltage is reading 0 the needle is stuck in the numb zone.

voltage was much closer but slightly over, ranging from 14.55 to 14.70, I overshot. goal was 14.5, shoudl be close enough, also unlike my prediction higher voltage makes the needle move away from the center not closer to it, center point should be the same.


Next vid should be better (of the modified gauge) , the frames will be evenly spaced and I will try not to trip over the tripod in the middle of the cook this time

[semlin]

worked for me. saved to desktop and mac preview allows me to click frame to frame. this is quite different from your earlier results. Do you think this is due to voltage? It looks like you lost 10 degrees out of the top end range and this revives the possibility that the 93-94 gauge will match... anyway here is my summary...

1. numb midpoint starts at around 170 (frame 15)
2. voltage actually hits zero at 187.5 (frame 22)
3. temp gauge possibly moves at 210 or maybe camera wobble (frame 29)
4. first positive voltage at 218 but no movement (frame 31)
5. gauge moves at 222 (frame 33)
6. gauge at 2/3 at 228 (frame 36)
7. gauge at 3/4 at 238 (frame 40)
8. top of gauge reached red at 244 (frame 43)
9. bottom of gauge in red at 250 (frame 46)
10. midpoint of red is 254 (frame 48)
11. top of gauge hits top of red at 259 (frame 50)
12 bottom of gauge out of red at 266 (frame 53)

I would discount the 210 result and say the gauge is numb when voltage is less than .05 millivolts.

I would also say the linear response is consistent. it looks like 135 to 145 (frame 1 to 5) is roughly the same as 250 to 259 (frame 46 to 50) although i am not as sure about 135 to 155 (frame 1 to 9) and 240 to 259 (frame 41 to 50).

[semlin]

more

[semlin]

and more

[RavenTai]

Originally Posted by semlin

this is quite different from your earlier results. Do you think this is due to voltage? It looks like you lost 10 degrees out of the top end range and this revives the possibility that the 93-94 gauge will match...

yes I do think it is the voltage, tunring off the battery charger (14.x vs 12.x volts) got a noticeable needle movement, closer to the extremems of hot or cold the more movemment. little or no movement closer to the middle.


Thanks for posting those saved me a lot of time in "Go live" a program I had not used until recently so the going is slow.

[RavenTai]

Ok got enough data to order resistors,

On paper the ideal resistor for centering at 200°F is 106.3 Ω >2watt


I have been looking at these wire wound 1% accuracy resistors (RS02B_______ the 3 watt version)

http://www.vishay.com/docs/30204/rsns.pdf

They do not come in 106.3 Ω but have some close values,

on paper these following resistors should center the gauge at....


82Ω......215°
100Ω....204°
110Ω....198°
120Ω....193°

and an oddity 75Ω......221°, not the ~210 to 215 I had read of the gauge earlier during the cook with the diode bypassed that cook was not ideal so I am going to go with this for now, I'll see what happens when the resistors are installed and try to figure out what went wrong.

These resistors are only $.82 each so I ordered 2 of each of the above values. Hopefully we can keep this as a 1 wire and one resistor mod but I ordered some low value resistors incase I need to adjust the range some (replace D1 (zener diode) with a resistor instead just of a wire)

One should be able to calculate needle position per temperature for each resistance as I do have the needle position per voltage across L1 but need read up on Thevenin Equivalents something I have not worked with before. Until I do I can only calculate for the balance or center point of the circuit.


Someone asked for the value of the inductors

L1 = 95.3Ω
L2 = 81.5Ω
L3 = 46.0Ω

These figures are direct measurements, observation of the circuit matches reasonably close to those values. Impedance via inductance is ignored as currents are fairly steady when the circuit is in use.

Here is the thermistor curve I am currently using (still a question mark here) , this is from the used one pulled out of the 95 Head, have not worked with the new thermistor yet, you will note they do not match Bill's nor Rich's findings, hopefully these are accurate, the only thing that can currently kill this project is if thermistors out there do not have the same response,

Temperature F/ Resistance Ω

261.8 23
260.8 23.1
259.8 23.2
258.8 23.5
257.8 23.8
256.8 24.2
255.8 24.4
254.8 24.9
253.8 25.3
252.8 25.5
251.8 25.9
250.8 26.3
249.8 26.8
248.8 27.1
247.8 27.6
246.8 28
245.8 28.4
244.8 28.9
243.8 29.3
242.8 29.7
241.8 30.2
240.8 30.7
239.8 31.2
238.8 31.6
237.8 32.1
236.8 32.6
235.8 33.2
234.8 33.8
233.8 34.3
232.8 34.8
231.8 35.4
230.8 36
229.8 36.6
228.9 37.2
227.8 37.8
226.8 38.4
225.8 39
224.8 39.6
223.8 40.3
222.8 40.9
221.8 41.6
220.8 42.3
219.8 43
218.8 43.8
217.8 44.5
216.8 45.2
215.8 46
214.8 46.8
213.8 47.5
212.8 48.2
211.8 49.1
210.8 50
209.8 50.9
208.8 51.7
207.8 52.5
206.8 53.5
205.8 54.5
204.8 55.5
203.8 56.3
202.8 57.2
201.8 58.3
200.8 59.3
199.7 60
198.9 60.8
198.0 61.7
197.0 62.9
196.1 63.9
195.0 65.2
194.0 66.4
193.0 67.6
192.0 68.8
191.0 70
190.0 71.3
189.1 72.5
188.0 73.9
187.0 75.1
186.1 76.5
185.0 78
184.1 79.4
183.0 80.9
182.0 82.3
181.0 83.8
180.0 85.4
179.1 86.9
178.0 88.7
177.1 90.3
176.0 92.3
175.0 93.9
174.0 95.7
173.1 97.6
172.0 99.6
171.0 101.4
170.1 103.3
169.1 105.4
168.1 107.5
167.0 109.7
166.0 111.9
165.0 114

Source voltage for calculations is 14.5

[RavenTai]

oops and the curve in viewable form

[semlin]

cool

At what temp below and above 200 degrees will 0.050 mv be on that resiter? From my observation from your Gif that is actually the range in which the gauge will centre. If the gauge response is the same as now you will be centred from 196 to 204 and you will hit red at 222 not 226?

[semlin]

sorry, I shoul elaborate, it appears to take a minimum of .05 mv to move the gauge off centre, but you are not taking that into account in your paper calculations. in your gif sequence both the positive and negative side the needle stays still for 4 degrees after it gets voltage. That means you actually get a 22 degree swing not a 26 degree swing before you hit red. I suppose you could play with this with a small resister on the diode, but if I am correct I would suggest instead a big resister that centred at 196.

[cary]

Originally Posted by RavenTai

Ok got enough data to order resistors,


and an oddity 75Ω......221°, not the ~210 to 215 I had read of the gauge earlier during the cook with the diode bypassed that cook was not ideal so I am going to go with this for now, I'll see what happens when the resistors are installed and try to figure out what went wrong.

Just a thought (from someone that is way over their head). It is likely that the factory used 3% or 5% tolerance resistors, and the one you have it near the edge of its tolerance range. You might check it to make sure it not slightly off.

BTW, the Vishay resistors are really good quality as are the Mills units.

[RavenTai]

Originally Posted by semlin

sorry, I shoul elaborate, it appears to take a minimum of .05 mv to move the gauge off centre, but you are not taking that into account in your paper calculations. in your gif sequence both the positive and negative side the needle stays still for 4 degrees after it gets voltage. That means you actually get a 22 degree swing not a 26 degree swing before you hit red. I suppose you could play with this with a small resister on the diode, but if I am correct I would suggest instead a big resister that centred at 196.

I see what you are saying,


To accurately answer how many degrees .05V change is I need to learn some more. But using strait ohms law it is roughly 4 degrees,

With the frames from the animated gif it may seam to be .05V before first movement but I have more frames at higher resolution here and it appears to have slight movement as low as .018 or .013 V on the high side witch would be about 1 degree, And maybe a little more on the low side or that may be just how the frames land out.

Semlin PM me an e-mail that can take large files, I'll send you some of the relevant original pictures and you can let me know what you think. Each original is ~1.3MB

[RavenTai]

Originally Posted by cary

Just a thought (from someone that is way over their head). It is likely that the factory used 3% or 5% tolerance resistors, and the one you have it near the edge of its tolerance range. You might check it to make sure it not slightly off.

Hmm that is actually a good insight, the 75 ohm resistor checks out at room temperature (75.6 ohms) but because it is at it limits wattage wise it gets dam hot in use especially when reading higher temperatures. I wonder if that resistor has a poor coefficient of temperature?

From the pics Semiln posted the 93 resistor looks much beefier

BTW, the Vishay resistors are really good quality as are the Mills units.

I am glad you approve as I have never selected resistors before and did not really know much about what I was looking for, I did some reading and wire wound resistors are suppose to be more accurate and stable over time than carbon film resistors and even metal film resistors, wire wound resistors do have inductance witch would cause problems in some circuits but that should not apply here as current are steady. The mill spec rating is a good sign also, just below aerospace and life saving equipment ratings.

[RavenTai]

Originally Posted by RavenTai

Semlin PM me an e-mail that can take large files, I'll send you some of the relevant original pictures and you can let me know what you think. Each original is ~1.3MB

actually this might be easier

originals

"save taget as" "save link as" or whatever it is on a Macintosh. should be 119MB probably a slow DL