Another Horn Question-74 Cj5

Sorry about the post, I was just trying to give him an option for an external regulator that would require only a crimping tool to make a fix incase he did not have a soldering iron and a roll of solder laying around.
That way if he was unsure about his skills with soldering all he would have to do is crimp on a couple of connections and he would be finished. If he had the speedometer out, it would probably only take him about a half hour.

The effect of ambient temp affecting the meter is still 'up in the air' so to speak .

I decided to an experiment.

The speedometer I was using for the mock was a Crown replacement speedometer but it gave me conflicting results.

I first checked the meter at room temperature
This way I can see the position of the needles to see how much they would move if any.


And then put it in my freezer at around 30*F.

You can see the temperature gauge dropped down quite a bit but the fuel gauge hung in there. If it moved at all it was just a smidge

I then took it out and put it in my oved set at 130*F ? To hot?


Again the temp gauge move quite a bit. But the fuel gauge stayed rigidly in place and I almost thought the gauge was stuck. but removing the power allowed the needles to drop.

I repeated the test a couple of times with the same results.

So I will have to wait until I have some time to put some stock gauges in a speedometer housing and repeat the test just to get back on track.

Again, sorry about the posting.

 

Love the experiment! Ha! And it’s good to have options! There’s always two ways to do something!

I’m starting to think my regulator is good, so I’m going to move to the senders and see what I get.

FYI...I’m a girl.

 

Interesting experiment.

IMO the main thing to test is whether the PWM action of the CVR compensates for the temperature sensitivity of the gauges. Maybe. This does not help you much if the CVR is kaput, but it would be interesting to know. Looking at the inside of one of these gauges combined with a CVR here Instrument cluster voltage regulator upgrade - Page 2 - Full Size Jeep Network shows two thermal elements, one is the CVR and I presume the other expands and contracts with power dissipation to move the needle. Both thermal, but different mechanical outcomes.

It's clear that the gauge action will be affected some by the ambient temperature (assuming my interpretation of the gauge innards is correct.) I wonder if the ambient temp affects the two elements in the same or opposite directions? The PWM action will change, but will the average voltage change? Both the heating and cooling part of the cycle will be changed, so ambient temperature may not affect the CVR output over time.

And why would the temp gauge be different in this respect from the fuel level? Both are getting the same voltage. Middle of the band for both is sinking about the same current (23 ohms roughly, with the regulated voltage, about 200 mA.) No obvious explanation for the difference?

 

Tim, I am a bit challenged when it comes to electronic work. After looking at the 7805 regulators on the Mouser site I became a bit confused on how exactly install on the instrument cluster. Do I need a wire plug in for the 7805 or are the terminals direct solder some way? Also there seems to be different configurations of the same regulators, which one is best? Thanks in advance, Jim

 

Jim, you want one of the 7805s that is in the TO-220 package. They are generic. I posted links to specific parts on the FSJ network thread from above: Instrument cluster voltage regulator upgrade - Page 2 - Full Size Jeep Network

I would solder direct to the leads. Cover those connections with heat shrink tubing if you want to. There is some discussion of this in that thread. The 7805 part is made for circuit board insertion, with a heat sink standing proud above. You will need to adapt it to your installation by soldering to the usual leads that go into the circuit board. Many of these parts ground through the mounting tab (but not all). If you pick a part with a grounding tab (and ground the tab), you can clip off the ground lead and only wire to the IN and OUT.

This may be more confusing... I would pick a part that grounds through the tab. The device must then be mounted to a grounded part of the cluster, wherever convenient. Then I would cut off the ground tab and put a solder lug through the attaching screw. The solder lug would provide a ground for the required capacitors.

Just an example - Solder Lugs for Amps | stewmac.com

or Connectors, Interconnects | Terminals - Solder Lug Connectors | DigiKey

I keep such things in one of my parts boxes. I'm sure that you can find them at Mouser or Digikey or AllElectronics or maybe a hamfest if you search - or make one from a scrap of copper. Not essential.

 

Thanks Tim, I have been studying the links you have provided. I now have a good idea how the CVR works and how the 7805 regulator works to replace it. However I am still a bit confused as to what the capacitors are needed for. Do the capacitors help the 7805 regulator maintain a constant voltage during large ambient temp swings? Or they needed just for reducing radio noise? I have no need for a radio at all.
Sorry for the questions, I am sure it is just me missing something.

 

This turned out longer than needed. Not a criticism of your question.

Not sure where to start. You could read the first chapter of Horowitz & Hill to learn a bit about circuits and passive components. This question was covered in the thread I linked on FSJ Network. That thread points to the application notes and/or data sheets for the 7805. That's the first best source - read the notes. That's like the package instructions. Major suppliers like Digikey and Mouser will link the data sheets on their site - it's up to you to download and read the instructions.

There are basically three passive components: resistors, inductors and capacitors. They have different performances in response to signals based on frequency. An ideal resistor is not frequency dependent. An ideal inductor conducts at low frequencies and blocks high frequencies. An ideal capacitor blocks low frequencies and conducts at high frequencies.

This frequency-dependent resistance is known as impedance Z. A capacitor across the input or output will short out any high frequencies and allow low frequencies to pass. You can calculate the frequency dependence of a capacitor from its reactance X = 1/(2 pi f C) where f is the frequency in hertz and C is the capacitance in farads. X + R = Z.

IF you read the instructions, you will see that you don't have to use the capacitors. You now kinda understand what the capacitors do electrically - that is, they short out high frequencies. This device is pretty much one transistor as a regulated voltage divider is not noisy compared to a switching supply like that little block shown above or your computer power supply. So you don't need the capacitors to protect the environment from the device. Instead, they are there to protect the device from the environment. They reject (short out) high frequency junk from the supply or the load.

 

Just a comment -

This book, https://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521809266/ref=sr_1_1 is very good and something of a phenomenon. Now in its third edition, it's expensive ca $100 and it has an addendum (the X chapters) and student manual at an additional charge. The second edition can be found used for ca $20 and should suffice for most readers. I have owned the 2nd edition for more than 20 years and it's still a valuable reference. Very readable. You could easily put together a course in practical electronics using this book.

 

Sorry for going on about this... somebody might find it useful.

This is from the STMicroelectronics L7805CV data sheet, and is typical -


and


I would look at this and say to myself, "Self, we are a long way from the battery and alternator. So we need the input bypass capacitor. We don't really care about transient response, so we could reasonably omit the output bypass capacitor." However, the output capacitor is something like 25c (more than I guessed above), so I'd include it.

These sheets will have a lot of numeric specs that generally don't concern you. They will always have a descriptive section with some text about how to use the part and what its limitations are. These sheets often have example circuits that you can copy verbatim and be fairly certain that they will work in your application.

www.mouser.com/ProductDetail/STMicroelectronics/L7805CV?qs=sGAEpiMZZMtUqDgmOWBjgNedF5UBsYhVzhrcsEyhlP4%3D - click on "datasheet."

What I would look at first-
1) Packaging. Lots of devices are only available as SMDs (surface mount devices) and are not usable unless you make a circuit board.
2) Pinout.
3) Description.
4) Example circuits.

Sometimes the numeric info is useful or interesting, like the voltage stability per degree C listed above. Pick out anything relevant. Packaging info is also at the bottom. For example, scrolling down to the bottom shows the package naming for the devices. They sell this in both grounded and insulated tab package. They show the TO-220 is grounded and the TO-220FP is insulated. Looking at the Mouser page, it's listed as TO-220, so it has a grounded tab.

 

Yes, I have measure the pulse width and frequency of the PWM and it does vary depending upon the temperature. This is easy to see just by putting test light on the "A" post and watching the speed and duration of the flashing speed up and slow down. It very obvious on a scope. I'll see about getting a video up on you tube if I have the time tonight.

It think I figure out the explanation for the fuel gauge is that the internal regulator was still operational although it was getting power from a different location. It's not polarity sensitive. It works if hooked to the "A" post or the "I" post. Sadly it won't help anything if power is connected to the "A" post.
So it would open and close cutting (shunting?) off power away from the fuel gauge keeping relatively accurate. Next time I will eliminate the internal PWM regulator from the gauge. I don't want to ruin a good one so I'l look for one I already pulled apart.

Did you know the stock gauges work with any voltage from 6 volts to 48 Volts. Well that's as high as I was willing to push the gauges. But they work fine. Just another cool experiment. Maybe I'll do another video for that also.



I did some ruff calculation with the thermal expansion of steel and copper bi-metallic strips. I have to measure the actual length but based on a length of roughly 0.0381 meters and a thickness of 0.00048 meters, bend of the bi-metalic strip with a temperature of change of 38*C will be about 2.87 mm. Say the thickness of 2 dimes. You can see by the construction of the needle to bi-metalic strip 2 mm will greatly change the position of the end of the needle. I'll have to measure it more when I get home.

So say the so lets say that the L7805CV is always putting out the same voltage so the current should remain steady and it always putting out 1000 mWatts. Then the temperature of the heating element that the heater windings is never going to change. But the ambient temperature around the bi-metalic strip is changing 30*C.

So lets assume it takes x*C to move the needle from rest at room temp to move 1 mm to center the scale. Lets say that it takes 50*F or 10*C.
We see that the ambient temperature is changing 30*C so now you have 30*C from ambient + 50*C from the nichrome heater wrapped around the bi-metalic strip for an combined increase of 80*C.
Well the CVR doesn't care about the temperature as shown in the specs. It will always put out 5.00000000000 VDC no mater the ambient temperature. .

However for the needle not to move with the increase of the temperature we actually need to REDUCE the voltage going to the gauge. Now it will need to put in some type of thermistor into the CVR circuit and adjust it so the voltage will increase with lower temperature and the voltage will drop.

You need a 'variable' CVR ( there's an oxymoron if I ever said such) to work with an external control so maybe a LM317M. Then you could play around with a thermistor and resistor to get the proper voltage or current reduction through the circuit.
They are about $9.00 ea.

 

Before I took a gauge apart, I would measure the current used by the CVR when it's not driving the gauges. I'd guess there's something on the order of 1/2 amp at 5V sunk through the gauges. Maybe more, maybe less. When you reverse the polarity of the CVR and drive it from the 5V end, it's no longer driving the gauges. I suspect the CVR with one end floating does not use enough power to change the voltage at the gauges.

No actual measurement, but the original CVR in my J20 (which was driving 3 gauges) would visibly bounce my aftermarket voltmeter. (The in-dash ammeter replacement with a voltmeter is another cool thing you can do to the FSJs.) With the CVR bypassed, the bouncing stopped. By John's description, the CVR was still in there PWMing away, but with no load to drive. The gauge bouncing went to zero, which implies a negligible effect from the PWM action.

If you want to do this thermal compensation thing, I think the 317 is not going to be sensitive enough to change output in response to a thermocouple. Maybe. The controlling current through the voltage divider is something like 50uA (?) which intuitively seems too hefty to drive directly. Maybe you need a FET too? H&H has a section on temperature transducers and thermocouple compensation using an op amp. This is not what you want specifically, but the there must be something online about power supplies that vary with temperature. Maybe the circuit diagrams of these ICs would give you some hints, since they contain temperature compensation to hold the voltage constant. You could likewise over or under compensate to change the voltage with temperature.

 

Yep, 50uA.
www.mouser.com/ProductDetail/Texas-Instruments/LM317KCT?qs=TB%2FQ0sBK%2FGcz1btw204Pbw%3D%3D

TI has nice data sheets, better than the STMicro one I linked above.

(Dang. Bad link before. Ok now.)

 

I was think more along of a NTC or PTC thermistors. We use these in controlling our Peltier Cooling devices on our PMT's
As you probably know they are resistors with a negative or positive temperature coefficient, which means that the resistance decreases with increasing or decreasing temperature.

Hook it up in a simple voltage divider system to control the regulator.

 

Yes, I see how that could work.

Where do you use photomultipliers?

 

We build machines to read the light output of TLD (Thermal Luminescent Dosimeters) material.
They give off light proportional the the radiation absorbed when heated. They absorb radiation the same way the human body absorbs radiation so they are useful to determine how much dose a person receive when working in a radiation area.
The light output is very low at low exposures to as bright as a lightning bug. We need to use PMT that are sensitive at the wavelength the LiF:Mg, Ti. and have a high dynamic range.
We have to cool the PMT to reduce the noise and lower our minimum detectability.

You have probably seen these TLD badges in doctors office where X-Ray machines are used.

That was in the past, Now I'm building neutron detectors

 

Please keep this discussion going guys. Having never studied electronics, a lot of your comments are somewhat confusing to me but I am learning a lot too. I am beginning to get the general idea of what I need to do to to replace my CVR and keep my factory installed gauges. For some reason I cannot open some of the links to the data sheets from the suppliers. It will simply say access denied . Maybe my old laptop operating system. Anyway I have not yet been able to make all my definite decisions on which parts I might need so I could have you guys verify my parts choices before I order them. So what I have learned so far.
:The L7805 (Mouser Part #
511-L7805CV) TO-220 package with the grounding thru the mounting tab, is what I probably need.
: Given the low voltage requirements of the fuel gauge, about 1.5 amps max, a ground thru the tab is good enough without an added heatsink. Just ground to the speedometer to housing mounting screw and allow the speedo housing to act as a heatsink.
: Not sure if my solder skills are sufficient to attach wires and or caps leads to the terminals of the 7805. These parts are not expensive so I can order extras in case I mess up some of them.
: Caps are not especially needed but might as well add them to improve efficiency of the set up.
:I think capacitor choice is ok as long as voltage rating is sufficient.
:Removing the center grounding lug of the 7805 would give me more room to make my solder connections for the in and out wires and the positive leads of the capacitors. the capacitor's can be grounded thru a solder lug placed under the mounting tab screw.
: Would it be any benefit to use a separate 7805 setup for each of the two gauges? (less load from each gauge for better heat dissipation)
Thanks very much for your help and please pardon my dumb questions, I am a bit of a slow learner.
Jim

 

This is interesting too. A 7805 power supply all ready to go. Just wire it up: https://www.amazon.com/SMAKN®-LM7805-3-Terminal-Voltage-Stabilizer/dp/B00RKY0NP6

 

Which links are broken? Some of the links on the FSJNetwork thread are old and the pages are gone.

No advantage to two devices that I see.

The 7805 all-in-one regulator would work. The chip itself is pretty tough, and contains internal protection from overheating etc.

I don't know exactly how much current the gauges sink, but most of it is through the sender to ground, I presume. There is a 1.5A version of the 7805 if you would rather. Here's one that's rated for 2 amps.
www.mouser.com/ProductDetail/STMicroelectronics/L78S05CV?qs=sepekKm5O7lXLQm2U%2FAl6g%3D%3D
A similar part, the LM340, comes in a TO-220 package rated at 2.4A:
www.mouser.com/ProductDetail/Texas-Instruments/LM340AT-50-NOPB?qs=sGAEpiMZZMug9GoBKXZ75%252BmFNJYHX7LMkAYKmFAb74c%3D
You can find higher amp ratings in other packages. I think the TO-220 is convenient for this application because you can mount the flat package to the local steel parts and solder the leads dead bug style.

Some random thoughts -

Dead bug style could put stress on the chip where the leads enter the plastic case. I would put heat-shrink over the joint to reinforce it and reduce exposure of the lead-in. I'd also tie down the wires close to the device so they aren't flopping around and stressing the copper on the device leads.

Mounting on the steel cluster back or body steel will provide an excellent heat sink. Use a little thermal compund to improve thermal coupling, if you wish. Left over CPU paste works well. If you worry, run the circuit for a while and carefully feel the IC. I suspect it will at worst be warm.

Regarding soldering, I would tin the lead and tin the wire, then sweat them together with a little extra solder. Extra flux, good tin-lead solder (Kester), hot iron, get in, get out. If you are melting back the wire insulation, you're too slow. Bad prep? Cold iron? These devices are comparatively tough, and you can apply a lot of heat for a few seconds.

You need enough heat capacity to melt the joint together (fully liquid) before the heat diffuses out of the joint and into the device, or melts back the PVC insulation on your wire. Any of your benchtop soldering stations will be plenty for this, if in good nick... and you don't use a massive wire that draws all the heat away from your iron. 18-20ish would be good.

Use stranded wire, the more flexible the better. Solid wire is only suitable for buss bars, house wiring and inside a chassis where it will never move.

You also need to position or hold the joint in place until it's fully solid. A melted joint is liquid and will not stay together on its own. If you move the joint while it's cooling you could get a "cold" joint with poor electrical connection, low strength (may separate later) and a satiny appearance. The tin-lead solder when it sets properly will be shiny. Lead-free solders (now in use in industry due to the disposal issues of boards containing lead) will have a different satin finish.

 

or this one designed for automotive applications. 5 Volts up to 3 amps.
It's waterproof, humidity proof, dust proof, short circuit protection.
https://www.amazon.com/gp/product/B...o00_s00?ie=UTF8&psc=1&tag=jeepforumconvert-20

 

That's a switcher, not a linear supply.