I'm a totally rookie at this, and I wish to get of from the right point. So I hope for some easy guidance :o
My idea is, that I'll make a digital speedometer on a 1" screen, to be mounted inside my 1/10th scale RC car.
I assume that the input to the speedometer could come from the ESC in my RC. The speedometer then shows how many volts the ESC sents to the motor, but will be showed in another scale on the display/screen: not from 0-7 volts, but from 0-140 km/t.
Also it should show a D (for driving forward, when the ESC is sending the car forward), N (for nor forward or reverse) and a R (for reversing).
Also in the same display/screen, it should show the actual voltage of my LiPo battery.
Is this even possible, and what components do I need for this project?
Measuring power is easy as you just monitor the battery voltage and current.
Lots of power doesn't always mean lots of speed due to wheel slip.
With a 2 wheel drive car you could measure the speed of one of the non driven wheels.
With a 4 wheel drive car I'm not sure how you get a reliable speed measurement.
I'm a totally rookie at this, and I wish to get of from the right point. So I hope for some easy guidance :o
My idea is, that I'll make a digital speedometer on a 1" screen, to be mounted inside my 1/10th scale RC car.
I assume that the input to the speedometer could come from the ESC in my RC. The speedometer then shows how many volts the ESC sents to the motor, but will be showed in another scale on the display/screen: not from 0-7 volts, but from 0-140 km/t.
Also it should show a D (for driving forward, when the ESC is sending the car forward), N (for nor forward or reverse) and a R (for reversing).
Also in the same display/screen, it should show the actual voltage of my LiPo battery.
Is this even possible, and what components do I need for this project?
Most, if not all, ESC operate by varying the pulse width of the output to the motors. What leads you to believe yours is different? An actual data sheet type information source for your ESC is necessary to even think of how to do what you propose.
Most people use wheel or motor encoders to estimate ground vehicle speed. Essentially, you are measuring the wheel RPM, which can be converted to velocity.
Wheels tend to slip during turns, so averaging the results from two or four encoders will give a better estimate.
You can get the throttle position and the DNR state from looking at the PWM signal going to the ESC.
Aside from wire you don't need to purchase any extra hardware to do that.
A couple of resistors will allow you to monitor the battery voltage.
Any arduino is suitable.
mikb55:
You can get the throttle position and the DNR state from looking at the PWM signal going to the ESC.
Aside from wire you don't need to purchase any extra hardware to do that.
A couple of resistors will allow you to monitor the battery voltage.
Any arduino is suitable.
but which arduino do I need?
Ofcourse the monitor/screen, but what else? Please have in mind, that this arduino is a brand new world for me...
you cannot get a speed signal from any part of the ESC, neither the PWM signal coming in from the receiver nor from the power lines from the ESC to the motor. What you then measure it throttle position, which is not relative to speed. Of course, if you keep the throttle still at a certain point, it will give a certain speed once stabilised, but it's not a speed reading.
Simple question, what car to you have? Please post make and model (or a picture). I have made a very simple speed reader a little while ago using a magnet on the wheel (just with a dab of hot glue) and a hall sensor. Using two sensors, or two magnets, can also give you direction.
But first, spec the car. Next, we can go into hardware. I think an Arduino Nano, two hall sensors, a magnet and two 4 digit 7 segment displays (TM1637) will get you going, but I need to see the car to know if we can fit it.
you cannot get a speed signal from any part of the ESC, neither the PWM signal coming in from the receiver nor from the power lines from the ESC to the motor. What you then measure it throttle position, which is not relative to speed. Of course, if you keep the throttle still at a certain point, it will give a certain speed once stabilised, but it's not a speed reading.
My thought was, that the voltage sent from the ESC to the motor, could be "translated" into km/h...
HugoW:
Simple question, what car to you have? Please post make and model (or a picture). I have made a very simple speed reader a little while ago using a magnet on the wheel (just with a dab of hot glue) and a hall sensor. Using two sensors, or two magnets, can also give you direction.
But first, spec the car.
It's a MST CFX, with a 27t brushed motor and 1.9 wheels...
HugoW:
Next, we can go into hardware. I think an Arduino Nano, two hall sensors, a magnet and two 4 digit 7 segment displays (TM1637) will get you going, but I need to see the car to know if we can fit it.
Fun project to learn, BTW.
Hugo
Can't it be showen on an ordinary screen, like ST7735?
The voltage sent from the ESC is the battery voltage. The ESC pulses it, short pulses for low power and longer pulses for more power. Google duty cycle.
Ah, a crawler like car. The chassis gives room to mount the magnet and hall sensors:
Just drill a small hole in one of the couplers going from the motor gear box to the transfer box, only as deep as the magnet you are going to buy, and glue in the magnet. Test with a hall sensor first which way around you should glue the magnet in. Next, with some hot glue, mount two hall sensors (https://nl.aliexpress.com/item/32820407777.html or similar) close to eachother and close enough to the magnet. Probably on the transfer case. Those sensors you can hook up to any arduino directly:
While you do that, share your thoughts on why using an ST7735, which is a full colour LCD, to show simple numbers. If you want to read them while the car moves, it does not seem the first logical choice to me. And since you're a novice (like me, BTW, still), I think a simple display is easier to start with. And you can always expand to full touch screen TFT's later.
Okay - now (yep, post from China to Denmark is always this long to arrive, but I'm not in a hurry) I have these items on my desk:
2 x 23676
1 x 26897
2 x 84784
2 x 84766
2 x 26904
and a 0.96" (8x160 RGB) monitor.
I have found out, that if I messure the power (plus/minus) given from the ESC to the motor, I get voltage from 0 to approx 8 volt, depending on the throttle given from my sender. This voltage I'd like to show on the monitor as a dial, with a range from 0 to 100, where 1 volt should give 10 on the dial, and 2 volt should give 20 on the dial, and so on... How do I create this dial?
This dial should cover approx 3/4 of the screen, and the last "free space" should be with messurements from the battery (2S 7.4v, 5000 mA): voltage and amps.
I hope the above makes sence, and some kind person will help me.
As stated previously measuring the motor voltage will only give you the throttle position, not the speed. Is this what you want?
If you measure the signal going into the motor you'll need to add protection circuitry so that you don't destroy the Arduino inputs with voltage spikes generated by the motor.
It would be easier and safer to just measure the PWM signal going into the ESC. This will give you the same information as reading the voltage going into the motor.
mikb55:
As stated previously measuring the motor voltage will only give you the throttle position, not the speed. Is this what you want?
If you measure the signal going into the motor you'll need to add protection circuitry so that you don't destroy the Arduino inputs with voltage spikes generated by the motor.
It would be easier and safer to just measure the PWM signal going into the ESC. This will give you the same information as reading the voltage going into the motor.
I actually don't care about the real speed, but I'd like the dial to show the voltage as it was "km/h".
Thanks for the warning about the voltage to the motor!
By the PWM, do you mean the plug from the reciever to the ESC?
If the wheel are black on the inside, you might put white dots on the wheel and use one of the IR sensor modules to measure the tire rotation for speed. If you get a board with a wifi chip, you might be able to have all the info displayed on your cell phone screen.
zoomkat:
If the wheel are black on the inside, you might put white dots on the wheel and use one of the IR sensor modules to measure the tire rotation for speed. If you get a board with a wifi chip, you might be able to have all the info displayed on your cell phone screen.
I do NOT need the current/correct speed - I just wonna have the dial to ACT like it is the speed, that are messured!
The dial should be at zero when my RC car is parked, and at 80 when the throttle is "flored"...
"I do NOT need the current/correct speed - I just wonna have the dial to ACT like it is the speed, that are messured! The dial should be at zero when my RC car is parked, and at 80 when the throttle is "flored"..."
Well, if this is just a pretend setup, that should be simple. What ever your control input is, like an RC joystick pot, just map the analog input from that to 0-80 and display that as mph.
