Hi, I'm in the process of creating an haptic compass belt. Even if I'm used to make my own projects, this one is the most complicated concerning the electronic. I tried to read a lot of data sheets but I'm still looking for people competent in electronic to make sure I'm not making stupid mistakes.
The belt will be based on an Arduino nano 33 BLE, wich incorporate a magnetometer. The Arduino will get what's the direction the wearer is facing, and then send the command to turn on the vibrator facing north on the belt. Each vibrator is connected to a dual type D flip flop IC (CD4013), which should allow me to use only 5 wires along the belt to connect all the vibrators. Also, I would like the belt to be self-powered. This is why I was thinking of connecting a small LiPo battery to the pins 14 (gnd) et 15 (Vin) of the Arduino, and at the same time connecting this LiPo to a charger ic (DFR0668). Is it possible ? And would it then be possible to use the belt when charging the LiPo ? Thanks for reading, and if you have any feedback it will be gladly appreciated !
for charging/using have a look at this module:
how much current will you need to draw for the vibrators? are those motors offering a freewheel diode?
This module allow me to connect the Arduino on the LOAD connector is that true ?
The vibrator is drawning about 80mA. What is a freewheel diode ?
I was planning to use this kind of motor : https://www.robotshop.com/en/solarbotics-vpm2-vibrating-motor.html
correct. the load is whatever will require energy from the battery
the spec for your motor does not say anything, so worth double checking
I don't think your CD4013 can drive 80mA. Not even sure the 3.3V pin can deliver 80mA either
Ok, so if the vibrator is just a simple motor, I will need to add a diode around it like in this diagram around L and R in the wikipedia article?
You were right I think. I checked in the data sheet of the CD4013 and saw DC input current, any one input : max10 mA
I found this picture on Arduino nano 33 BLE data sheet.
Does it mean that it can provide enough for my project ?
Do you have any idea of solution for me about the CD4013 ? Is it possible to send less than 10mA to the CD4013 and use it to switch some kind of relay with 80mA to the motor ?
you could use mosfet + protection diode and wires directly to the motors to the battery (and enable/disable the connection with the mosfet) - of course that would mean more cables in the belt. How many vibrators do you plan to embed?
oh yes very good idea !
I was thinking about 30. Some researcher already done one with 32 and the more you're having the more natural it will fell in the end.
I plan to order a flexible PCB to fit all the connections, do you think it's possible to send 80mA through it ?
If I understood everything right it will only require one more wire along the circuit, the 80mA one, as I already have a Gnd and the base of the mosfet will be the output of the CD4013. Right ?
I don't know enough about flexible PCB but I suppose it depends on the size of the copper trace
The idea would be to get rid of the CD4013. if you don't have enough pins, you could use a port expander like MCP23S17 and the MCP23017 to drive the gates of the transistors
Why don't you think CD4013 would'nt be good to drive the transitors ? Aren't the port expander doing kind of the same job but all in one place ?
It’s an old proven technology, you can surely make it work, but it requires more programming work and wiring / possibly extra hardware than a simple ready made pin extension module.
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