VSS activated switch

roger55 said:
mrvette said:
HUmm, interesting, I have to do some checks on that, plug my DVM into the leads and see, got my curiosity up....I have heard many times the fans draw almost no current at speed, which makes sense to me...but...well...never did a test, ...
:huh:
Click to expand...
Yes, it would be interesting. I've been thinking about it a little more since I posted my opinion too. It's been a long time since I took physics. Does a brush type of DC motor use more current under a heavy load versus a lighter one? My first reaction is that it is the same but now I'm not sure. Maybe it will use less with help to push the blade. I still believe the fans would turn much slower by the windmill action versus being switched on. We've got some 80 mph speed limits here in Texas on I10. Maybe they would turn fairly fast at that speed. I'll be interested in your results if you do a test.
Wouldn't this little gizmo be good to have for that?
http://www.powerwerx.com/tools-meters/watts-up-meter-dc-inline.html

Edit:
A little more thought towards the load/no load thing. The brushes of a permanent magnet dc motor will be in contact with the stator windings for the same amount of time at any rpm or load. And the resistance in the stator remains constant. Therefore the current draw will be the same. Any EEs out there? Am I not considering something?
Click to expand...

If the motor is not doing any work, the current will be much less, now at what speed it actually turns into a generator, I dunno, I have my dual spals on the car and a common ground I can easy unbolt and run some leads through my DVM, my curiosity is up.....

I know one thing, any brush/DC motor that runs without load...say take the blades off, that thing will wind up super high speeds, IF the armature hangs in there, it goes to the point the inductance of the windings will take over in switching, drawing nearly no current....at what speed that is....?? I dunno, just I know the effect is there....

I need a good project for my curiosity .....

:bump:
 
Based on this,
http://en.wikipedia.org/wiki/Brushed_DC_electric_motor
it appears that you are right on the principle of the current being less on less load. So, the question is how much less?
It would be interesting to know what the reduced percentages would be a various highway speeds.
Of course, every car will be different. Air dams, grill design and so forth would affect the air flow through the radiator.
 
Last edited:
Resurrecting this thread because I was just now getting to hooking that SAS speed activated switch hooked up to my VSS to control my T56 reverse lockout.

Well, it doesn't work. Don't know what is wrong and just sent an email to the company. I actually bought 2 of these units and neither works. I'm guessing it's not compatible with my VSS. The VSS on my T56 is a 2 wire inductive type where one of the wires goes to ground.
My VDO electric speedometer and Dakota Digital cruise control both work fine off this VSS.
I do not have the VSS hooked up to an engine ECM.

So, for now and maybe permanently, I have just hooked up the reverse lockout to the brake light switch. As was pointed out earlier in this thread, the only time you might have to be careful doing this would be when shifting from 6 to 5 while braking (it would be very unlikely to accidently move the shifter to the right doing that). You would never be braking when upshifting so it's not an issue there. It was also mentioned earlier in this thread to use a clutch switch as well. There's no point that at all. The clutch is always depressed when shifting the transmission.

I may have wasted good money on these SAS switches. I was going to use the second one to disengage my radiator fans above 40 mph. I guess I'll scrap that plan for now.
 
Last edited:
I think I saw something over on CF recently about some guy that is making GPS speed based torque converter lockup switches. While its not tied to the vss in the trans it seems like it might be usable in this situation.

Also, the reverse lockout is still just wired to the brake switch on my fathers car... No issues with it so far :clap:
 
Last edited:
or you could just use an ardiuno to count the pulses from the vss on an analog input and have it close the relay after the pulses fall below what ever number is equivalent to 3 mph.
 
pancake said:
or you could just use an ardiuno to count the pulses from the vss on an analog input and have it close the relay after the pulses fall below what ever number is equivalent to 3 mph.
Click to expand...
Sounds like a better idea.
But, what does it take to build something like this?
 
There are other guys on here that are much better than me with i/o boards, but I do not think it would be all that difficult. Arduinos are open source so other people have probably already built it.

Here's a link to a sketch that counts pulses:

http://www.arduino.cc/playground/Main/EEM12L-32AKWhMonitoring


You'd just have to do some reading on I/O control with their programming language.

You can start researching here: http://www.arduino.cc

I think you could get away with an arduino mini if the processor will keep up with the pulses.
 
This is something that I probably capable of doing with enough time and effort but am just not willing to put that kind of time into.
I used to do a lot of coding when I worked but I've been retired now for 4 years and am not interested in getting back into it.

Hey I got an idea. Why don't you build them and market them? I'll be your first customer.:thumbs:
 
I want to swap a t56 into my car eventually it wouldn't be a pointless effort. I do not think the Arduino license permits selling devices so I'd have to find another platform.. I think one by the name of Raspberry Pi would work.
 
pancake said:
The t56 VSS does 17 pulses per driveshaft revolution, or 4000 pulses per mile. Just in case someone else wants to tinker with this.
Click to expand...
Pulses per mile depends on rear-end ratio and tire-size.
The T56 Magnum VSS in my '55 Bel Air with 3.55 gears and 28" diameter rear tires is 31,300 pulses per mile.
 
Last edited:
pancake said:
Does it have the Viper VSS or a GM VSS?
Click to expand...
The Magnum is an aftermarket T56 based on the TR6060.

The VSS has 2 wires and one of them I grounded. So, it is an inductive 2 wire type.

The engine is a RamJet 350 and uses a Mefi4a ECU. It does not require a VSS signal. I'm using the VSS signal for both my VDO electric speedometer and my Dakota Digital cruise control.
 
The reason I asked was the the GM units are 2 wire, and the Viper units are 3 wire VDO.

I only looked for info on the GM VSS, which like the T5 is 17 pulses per driveshaft revolution.

(28" tire diameter / 12) * 3.14159 = 7.330377' for one tire revolution

3.55 final drive * 17 pulses per driveshaft rev = 60.35 pulses per wheel rotation

5280' / 7.330377' = 720.2904 wheel rotations per mile

720.2904 wheel rotations * 60.35 pulses per wheel rotation = 43469.52612 Pulses Per Mile

Which is totally contradictory to what I posted above!
 
Last edited:
I think your math is right.

So, either my VSS is not 17 pulses per tail shaft revolution or my VDO electric speedometer's report of 31,300 pulses per mile is not accurate.

Without a doubt, the VDO speedometer does state that (I just double checked it) and my gears are 3.55. My tires are 28" inch in the specs but that doesn't account for the loaded radius. The actual number of revolutions per mile of the tire is probably higher than 720 accounting for that.

I did calibrate my speedometer using a Garmin GPS so it is calibrated correctly.
 
Yea, I figured the loaded tire diameter would be slightly different but I didn't think the differences in pulses would be as significant as 13,000.

I'm going to assume your VSS puts out something different than 17 pulses per driveshaft rev.
 
You must log in or register to reply here.
Top