designing a wireless speed controller

hello everyone I really wish you can help me with choosing a suitable sensor.

I want to rotate a shaft then a sensor would measure the angular displacement of the rotating shaft then transmit the readings to Arduino where I could use those readings and convert them to an output PWM signal.

**what I need ) **
1-) I need your advice on what sensor should I use that can measure angular displacement and at the same time that sensor should give an output that can be transmitted wirelessly.
2-) what transmitter and receiver I should use

any information can be helpful

you want a position encoder. for example, a disc that generates numbers with increasing precision when reaf from inside to outside:

how it's used:

and a way to read the markings. you would think robotics guys would be all over this. nope.

the HC 12 module sends serial data continuously. LoRa modules send packets, which would make for abrupt and choppy motor control.

LoRa is limited to a certain amount of data per day. Specially licensed spectrum. Doesn't make sense for an RC project which should be within line of sight to begin with.

nRF24 is another option for RC.

I don't know where the PWM comes in, shouldn't be before the signal has reached its final destination, so after the wireless transfer.

For the input, encoders are one option, a pot is another. Depends on what you really expect from your control. Continuous rotation? Absolute position reading?

The wireless connection should be continuous, as in have the transmitter send the commands over and over again. This way the receiver knows when signal is lost, and can take appropriate fail safe measures (such as stopping an RC car).

2-) what transmitter and receiver I should use

That depends on the distances involved.

For UHF devices 433Mhz to 915Mhz normally, there are very often legal restrictions on duty cycle (how much time the transmitter may be on) of 1% or 10%, which may not be suitable for responsive RC type applications.

There may be exceptions to these UHF rules specifically for RC model type use that allow continuous (100% duty cycle) use but in the UK for instance you are then limited to a signal bandwidth of 25khz. HC12s are popular in the Arduino world, but there is no mention in the datasheet I can find of the bandwidth or deviations used, so the device might not be legal to use.

UHF LoRa devices can operate at 20khz bandwidth so in the UK at least, can be operated at 100% duty cycle but at that bandwidth the maximum data rate is circa 1kbps, probably not enough for RC applications.

Things are much clearer for 2.4Ghz operation, its basically a worldwide frequency allocation and few if any duty cycle restrictions. If distances are short, less than a couple of hundread metres say, then the nRF24 devices are a reasonable choice, well known and with lots of examples.

If you need longer distances, say a couple of km line of sight at 2.4Ghz then LoRa devices are probably the only (legal) option and capable of sending a 8 byte RC packet in 900uS with LoRa and in 100uS in FLRC mode.

thank you all for the valuable information. but maybe I couldn't clearly explain myself I wanted to only measure the angular displacement ( how much the shaft is rotated ) so I can send this reading to Arduino and according to this, I will set the rotational speed of the motor. anyway, I found that a gyro sensor is useful for doing this task. yet still searching for how I can transmit the signal.

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.