This Blog is not dead, we are preparing a return with a renewed focus.
We made a few mistakes in presenting this material:
- We feel we operated in a vacuum
- We designed this EV Drive on our own, without community support
In the future, the Sanderson drive will be renamed the Open Source Automotive Dynamic Drive or something similar as we want our follower community to assist & contribute in its development.
Power Regulation on the Maple
Power regulation on the Maple is provided by two low dropout linear voltage regulators. (The part is the MCP1703 from Microchip, in the SOT-23A package. You can download the datasheet here ). One of the regulators supplies power to the digital voltage plane; the other supplies power to the analog voltage plane.
These voltage regulators nominally take an input of up to 16V. In addition, while the maximum continuous output current for the board is 250mA, if you are powering the board off higher voltages the amount off current it can supply goes down, due to the regulators needing to dissipate the extra power. So if you are powering the board off 12V, the max current is about 40mA at room temperature. In general (again, at room temperature) the max power dissipation (PD) for the chip is about .37W, and output current = PD/(Vin-Vout). For exact max current calculations, please refer to the datasheet linked above.
If you are planning to draw a lot of current from the Maple board, it is necessary to provide input power as close to 3.3V as possible. Powering the microcontroller circuitry and LEDs on the board alone takes approximately 30mA, so if you are powering the board with 12V that leaves only 10mA (at best) available for powering any user circuitry. Attempting to draw more than 10mA runs the risk of shorting out the power regulators and bricking your board.
Well, after replacing the 2 Mosfets & 2 Opto-Couplers & adding a light bulb to the transformer (to act as current limiting device), and double-triple checking the board, we felt safe enough to connect Leaf Maple #3 to the Sanderson Drive & apply power. And… it worked… for a while… Pouf! 3 Dead Leaf Maples so far & more troubleshooting before we can move forward…
Found out tonight as we were doing preliminary tests before integrating the whole Duino Communication Network (built over the last few weeks) that our last Leaf Maple blow-up has caused some collateral damage caused by runaway voltage. It seems we need to at least replace a pair of Mosfets & Opto-Couplers.
How do you like 4 Duinos sharing power & ground?
So, tonight we now have the Arduino Mega in the center providing power & ground to everyone else (via his over-sized custom communications shield) & coordinating 2 serial communications. He will also coordinate I2C with TFT Touchscreen LCD when we add that piece of code.
On the left is the Leaf Maple (32 bit Arm Cortex) snapped on his communication shield, almost ready to be dropped in place on top of the Sanderson Dynamic Drive. Expect this within a few days…
On the top right, we have the Arduino Nano hidden behind the 4x20 LCD that already displays Requested RPM & Effective RPM.
On the Bottom right, we have the Arduino Uno behind the 320x240 Touchscreen TFT that is ready to send the “Start Engine” message, but nobody is listening yet to his I2C chatter. We will work on that over the next several days…
Next up, will be to connect the Arduino Pro/Mini (in his pill bottle) that runs the hall effect sensor counting the rotations of the 3Phase AC motor shaft.
This is what will actually give us the exact RPM performed by the electric motor.
Before the Electric truck hits the road, we still need to design an “alternator” to charge the 12Volts battery that powers all these Arduinos & a Charge Controller that monitors the charge of the 10 to 20 12Volts Lead Acid batteries in the pick-up bed.
Stay tuned, lots of development happening over the next 30 days!!
Guess what we are doing tomorrow night?
We are now ready to test the Leaf Maple Communication Shield on the Sanderson Dynamic Drive, then connect it to the Arduino Mega & his own Communication shield. Hopefully this pair should talk right off the bat so we can then add the Hall effect Nano that counts Motor revolutions and then the LCD that displays the values and/or the TFT that unlocks/starts the motor. Busy night ahead of us!
Time for a Mega Shield…
While its nice to have a brand new shield for the Leaf Maple, the Arduino Mega that will talk to everyone also needed an easy ability to connect all Serial ports & I2C for easy/reliable 2-way communications with everyone else. So we decided to also give him his Custom (Communications) Shield.
2 Shields conceived, designed, drawn, printed, ironed, etched, drilled & successfully tested in 24 hours! Katchow!
Time for a Leaf Maple Shield!
So, we realized that using the Voltage Regulator of the Leaf Maple to power up all other required Duinos (Uno for TFT, Nano for LCD, Pro/Mini for Hall Effect sensor & Mega to communicate with everyone + probably another Duino to act as Charge Controller & monitor Battery Voltages) was asking a lot for a tiny built-in (Leaf Maple) Voltage Regulator.
Create a Shield sandwiched between Sanderson Dynamic Drive 2.0 & the Leaf Maple that controls it & that will provide power to everyone and take care of all communications. Of course, one important requirement was to have this shield translate serial communications between the 3.3V level of Maple to the usual 5V level of Arduino Mega.
Success: Within 1 evening, the shield is done, tested & working!
Trio of Arduinos talking:
The Mega on the left acts as she is receiving the exact RPM count from the Hall effect sensor & passes it to the Leaf Maple in the Center which uses it to figure out the exact power dosage to the motor & transmits this, along with the value from the pot box (gas pedal) to the Arduino Nano hiding behind the Parallel 4x20 LCD display.
Prototyped the Hall effect sensor to determine if it can reliably count how many turns the shaft of the motor executes. We now have a reliable way to know the exact RPM of the motor. We will need to find a suitable enclosure for this dedicated Arduino Nano with Hall effect sensor probe & incorporate this additional feedback.
We worked on communications this week-end. Master Node (Mega 2560 in the center) sends via I2C the Voltage level to the Uno running the TFT Touchscreen that will be mounted in the dashboard.
The Master Node now can also receive via one of it’s hardware Serial Port Amperage level data from the Mega2560 on the left (stand-in for Leaf Maple).
Next step is to figure out how to send both Amperage & Voltage via I2C and extract both data points. Then RPM data can be added to the data stream.