Please forgive any terminology errors, or damned stupid questions I may ask, an Arduino newbie here.
I am looking a the feasibility of using an Arduino to control the speed of a brushless motor, with the speed being determined by a hall effect input.
It may help if I explain the application; I restore vintage cars, and I try to keep a lot of the originality in the visual aspects as possible, this includes the gauges. Now, with vehicles that have all original gauges, engines and gearboxes this is not an issue, I replace the cables/cable drives accordingly and everything works (in a fashion). But, I have the occasional project that I swap out engines and gearboxes for more modern units, give the car better brakes as well as other sensible modifications, but I want to keep the period correct instruments.
I have the option of gutting the gauges and retro fitting the internals with modern units, which I do not want to do. Or I can convert them to use more modern electrical drives and drop the drive cables. This will allow me to keep the gauges intact and original and if required revert them back to original.
So, for example I have a car here that I want to fit a 1960's Smiths Chronometric rev counter to, which originally would have used a cable drive. But the engine the customer wants does not have a mechanical pick up.
My question is, is it feasible to add a hall effect sensor and Arduino to detect the engines RPM, then for the Arduino to control a brushless motor to mirror the speed of the engine?
The reason i say brushless motor is that the engines I am using reach speeds of 6 to 7000RPM, and as for a hall effect pickup I see this as a cleaner option than using the ignition trigger on the coil which is horrendously noisy.
So to the collective expertise, is this feasible or should I have a stronger cup of coffee and stop having stupid ideas?
Not clear. To me. Is this an indicator for RPM like a tachometer or some kind of engine wear counter?
How important is accuracy? If it is “just” RPM this is feasible if you can live with some error, still feasible if you want higher accuracy or perhaps most rapid response. But a bit more challenging.
Picking up the hall effect and processing that no large deal.
Control little brushless motor like in r/c cars or quadcopters no large deal.
Getting a good rapid and faithful tracking of the one to the other is more of a challenge but nothing that hasn’t been done before.
maximum RPM would be 6000 rpm, that is a hard set physical limit on the engine. As for load, it takes minimal force to operate one of these gauges.
as for minimum RPM, realistically, the engines tick over between 500 and 1000 rpm. So below 500 is pointless measuring as the engine will struggling to run or even stalling.
Am I correct in thinking I am going down the right route with the brushless motor and not using a stepper motor due to speed limitations? As or feedback from the motor, are we talking a unit with hall effect speed sensors built in? In my limited knowledge, something like a PC fan
I think you are going to have to experiment. The inertia is going to kill any acceleration/deceleration of the tach display. I suspect a simple DC motor will be just as effective as a brushless motor.
Paul
Modern ESCs and quadcopter brushless motors will handle the inertia. It is necessary in the case of quadcopters that the motor reach the RPM requested by the control loop as quickly as possible. Dynamic braking is employed.
@saxton67 by open loop I mean just letting the ESC control the brushless motor, no feedback into your system to compare and correct.
This prompted the accuracy question. I think you can do maybe OK enough this way. I can see perhaps needed to put in a translation/correction/calibration curve or calculation.
+1. Sounds like fun.
google
quadcopter brushless motor
and
quadcopter ESC braking
For some inspiration. The little motors are amazing and come in a variety of sizes and RPM with respect to voltage. The ESCs can (still) be controlled by the old fashioned servo signals; in a higher performance version of this project you might switch to a 21st century control protocol.
Brushless motors will last a long time in this use scenario.
I have converted several gauges (water temperature, tachometer) to electronic use with more modern electronic fuel injected engines by replacing the "guts" of these gauges with modern gauges from Autometer. Sounds like you may have done the same. The speedometers/odometers are more difficult to convert so I use a device called Cable-X to convert an electronic signal to a cable drive. The Cable-X is rather expensive but there are other, less expensive, devices that do the same thing. You should be able to drive your old Smiths tachometer with one of these units.
