But the 3 gauges are paralleled together so that would be 4.2 Ohm load not including the R of the 3 senders.

 

It has been a while since I played with series and parallel circuits, but I'm pretty sure you can treat each gauge/sender pair as a separate circuit. In other words, we know the source voltage, the gauge resistance, and the sender's max resistance. E=IR so I=E/R. IOW, divide the combined resistance of the gauge and sender into 5 and you'll have the current of that pair.

That's what I've done in the spreadsheet on a per gauge/sender basis. Picking the max current value for each pair gives a total of roughly 1/2 amp.

 

I'm skeptical that it's going to work satisfactory without some sort of potentiometer installed for adjustment of the output flow.

Without it for tweak adjustments, I foresee too low or too high of readings depending on vehicle.

 

You can do that yes. The power source from the IVR, to the separate circuits or gauges. As long as the values of the separate pieces are known you can treat each section as separate.

Or you can treat them all as one circuit from the battery to the IVR to the gauges.


Just like one whole city block may be on one circuit from the power plant, there are many more circuits in your home on that block. Many circuits can branch off from one "main" circuit etc...

Ford treats them as one circuit from the IVR to the three gauges, and separate circuits from the gauges to the sending units.

 

I'm pretty sure the readings won't be too high. Somewhere I've read that the IVR was supposed to give the equiv of 5.2 volts, so if that's true Don's 5.0 will give less current and slightly lower readings. But, I'm going from memory and that is dangerous. Anyway, I'm hoping his approach works well since it is a lot simpler than the adjustable one I planned to try - some day.

 

Bingo. While the EVTM may say 5v for the gages, I am thinking they need somewhere between 5v and 6v. Here is a pic of the gages with the truck warmed up.




All my gages are reading lower than before. The oil pressure and temp are both reading a full letter lower or more and the tank was just under full. I am wondering if the grounds are contributing to the low readings.

Sorry about the delay. Got sidetracked mowing the yard, taking the trash out, etc.

I also repainted all the needles with Safety Orange.

Going to look into an adjustable voltage regulator. My truck is the guinea pig for this experiment.

Anybody notice the Autometer Sport-Comp Voltmeter?

 

So, Plan B? Adjustable regulator? I'm thinking we put a big capacitor on the output of the IVR to turn the square wave into pretty good DC. Should give the same current and therefore the same gauge readings as before, but we can read the voltage accurately with a DVM. Then we set the regulator for that.

 

A big capacitor on the IVR would keep the gages on for a while after you shut off the truck.

Also, just how much current would it take to charge the cap and would that overload the IVR?

 

I like that Autometer Voltmeter.

I was afraid of the too low or too high scenario. hmmm...

 

Maybe I should be more clear - I wouldn't suggest using one of the caps they use in audio systems now, as those things are more like batteries and would load the IVR. Maybe a 100 to 1000 microfarad electrolytic, and that wouldn't provide too much load on the IVR nor keep the gauges on long.

I could try it with the instrument panel on the bench and put the scope on to see if we have DC. But, if you switch your DVM to AC and don't see anything then you have pretty decent DC.

 

After installing a 1 farad cap in the son-in-laws car for his amp, yeah that is what I thought.

I am going to look into an adjustable power supply, unless I can find a 5.2v fixed...

 

Not to discourage you from your quest.
But Dennis Carpenter Restorations sells these Regulators for $15.
Dennis Carpenter Ford Car, F-100 Pickup Truck, 8N, 9N Tractor and Cushman Scooter Restoration Parts

 

I did notice the voltmeter...I like it!!! I left my Ammeter in place and installed a separate voltmeter...but I like the look you have better.

 

Country, I have several IVRs. This quest is to find/make a regulator that does not float. I did come across a few schematics, but lots of parts. The quest continues.

 

Don - I'm not sure this will work, but I think you can raise the voltage .7 volts by placing a diode between the regulator and ground. Most diodes have a .7 volt forward voltage drop, so using a 1 amp unit would bias the regulator up that much.