The eChook Nano kits will shortly be back in stock at Greenpower, alongside a minor version bump to V2.1.
What’s new?
The main change for V2.1 is a revised PWM output circuit.
The circuit in V2.0 was an active pull down with a high impedance pull up, and a high output impedance of 1kOhm:
This circuit will interface with a 4QD speed controller that has a very high input impedance, but many PWM drivers have a higher current requirement, and pulled down the 5V output to a much lower voltage when connected. To improve on this, the eChook Nano V2.1 uses a totem pole MOSFET configuration, in the form of a MOSFET gate driver IC, to actively drive the output both high and low:
This provides a much stronger output that will interface with the majority of PWM motor drivers available. The 100Ohm output resistor (R15) is a compromise between low output impedance, and protection.
The short circuit current (if the PWM out is shorted to ground) is 50mA (I = V/R = 5/100), which the MOSFET driver IC can maintain continuously, so the PWM output is short circuit safe.
In a reverse current scenario (if the PWM output gets connected to a higher voltage, assumed ~24V worst case), this is limited by R15, and fed to the +5V rail through Diode 2 of the BAT54S Schottky diode array. This results in 190mA flowing though the Diode, just below it’s continuous rating of 200mA. It gets warm, but will withstand a continuous short to 24V.
Other Board Changes
The other main change is dropping the DCDC power regulator for the 5V rail from a 1A module to a 500mA module. In testing I have never seen an eChook Nano board draw anywhere near 500mA on the 5V rail, 1A was always overkill, and with the new power rail protections introduced in V2.0 this is a safe, slightly lower cost substitution.
Visually, the mounting hole for the Bluetooth module bracket now has a soldered pad around it as a quick visual identifier to distinguish V2.0 and V2.1.
V2.1 Greenpower Kit Changes
There are a couple of small tweaks to the Greenpower kit for V2.1.
The connectors and wire included for the current sensor and magnet sensors has had an upgrade. Previously it was 26AWG as that was what was available on the market. The V2.1 kit uses thicker 24AWG wire with tinned ends which is a more expensive custom wiring order, but the increased usability and robustness is worth it in my opinion.
The magnets have moved back to a 5x1mm Neodymium Puck magnet, from the more fiddly 3x1mm magnets in the V2.0 kit.
The HC-05 Bluetooth modules included with the kit run a newer firmware version than those supplied with previous kits, and eChook code version 2.04 is required for this module.