Help with mc34063a

[mvictoras]

This is awesome, thank you very much spec!

Questions:
(1) All of the above are breadboard friendly, right?
(2) How do I charge the batteries?
(3) Which program did you use to make the above schematic? Was it Eagle? Also to calculate the capacitors and resistor values, did you do it by hand or did you use software?
(4) What is the OV Supply Line? I am assuming that is GND?
(5) The PCA9685 in the schematic is the 16-channel PWM Driver, right? Or am I replacing that with the PCA9685 chip instead?

 

[spec]

This is awesome, thank you very much spec !

No probs mvictoras (most of the groundwork had already been done by you and the other ETO members)

Questions:

(1) All of the above are breadboard friendly, right? A breadboard would not really be suitable. Best build as a module contained in a metal case. I will give this some thought.

(2) How do I charge the batteries? With a twin channel LiIon charger. The batteries can either be charged in situ or taken off the Vibration Motor Controller (VMC) for charging. LiIon chargers are freely available, either as mains-powered, stand-alone units or as DC-driven small boards which could be built into your VMCs.

(3.1) Which program did you use to make the above schematic? Was it Eagle? Yes, EAGLE Light (free version). I have not been using it for long (did use more advanced ECAD at work) but it is surprisingly easy to learn and use, although I have only done schematics with it. I use MicroSoft Word draw for block diagrams etc.

(3.2) Also to calculate the capacitors and resistor values, did you do it by hand or did you use software? I never use software to design unless absolutely essential, large digital arrays for example. There was very little calculation involved. The capacitors are all standard-practice values as is the PMOSFET gate stopper. None of these values are critical. The only minor bit of calculation was the pull up resistor on the gate of the PMOSFET, the drive voltage for turning on the PMOSFET, and the battery duration.

(4) What is the OV Supply Line? I am assuming that is GND? Essentially yes, but being picky GND (ground) is not correct. In general, there are three earthy levels, '0V', 'chassis', and 'ground' (or 'earth'). All three of these earthy levels have separate schematic symbols. But you will see ground and chassis being used for all earthy levels on schematics. By the way, in the physical world, there is no such thing as a single level on a length of wire, PCB trace, ground plane, or chassis. They are are at different voltage levels and different impedance. In fact, a schematic is a gross oversimplification.

The earthy lines are one of the most critical areas in any electronic circuit. They are the foundation on which the circuit operates so it is vital to get them right. 0V (xxx) is the best way to label any particular 0V line. Thus you may have 0V(5V), 0V(12V), 0V(-12V), 0V(analog), 0V(digital) and so on. If you take an example of a class AB audio amplifier, you can turn the best audiophile design into a distortion generator by simply getting the earthy lines wrong. Circuits may oscillate and generally be unpredictable with the wrong earthy arrangements. Some RF circuits simply will not work.

Your VMC circuit would be low to medium susceptibility, but MOSFETS can easily turn into 4MHz to 6MHz oscillators if the layout is not right. The PCA9685 could also suffer serious ringing without care.

(5) The PCA9685 in the schematic is the 16-channel PWM Driver, right? Or am I replacing that with the PCA9685 chip instead? 'Chip' was a slip-up and was not intended. The PCA9685 module, as you selected, will be the best approach.

spec

 

[mvictoras]

ERRATA
(1) Fit rectifier diode (to be defined) cathode to drain and anode to 0V for each PMOSFET (catching diode to catch voltage under swing caused by motor inductance when PMOSFET turns off).

What does this mean? Is there an extra diode I need to use?

 

[spec]

What does this mean? Is there an extra diode I need to use?

Yes, one for each PMOSFET (motor).

It protects the PMOSFET and gives better motor control. It was an omission from the original schematic. As I have said many times before on ETO, I always make mistakes.

spec