The goal of this project is to create an automated power supply to support small-scale anodizing. By “small-scale”, the output is in the range of 10-15A; this is sufficient for anodizing surfaces of around 1 ft^2 at 12 ASF (amp per sq. ft), or up to around 3 ft^2 at “low current density” (LCD) rates of about 4.5 ASF.
The user interface is via a web page served over WiFi. The pages are simple HTML--no Javascript, etc.
The power supply is automated and performs the following:
- Given ASF, surface area, ramp time, and target thickness, calculates current, total time, estimated peak voltage, and estimated peak resistance.
- Ramps up the constant current to the target current.
- Stops the current and signals the operator if the time is up or (if enabled) a decrease in resistance is detected (i.e., peak anodizing resistance or PAR). The latter has been claimed by some to provide a much more reliable method of maximizing layer thickness independent of electrolyte condition, temperature, etc.
- Generates plots in real time of the voltage and current.
- Generates numeric data points for voltage and current (can be copied to a spreadsheet for analysis or plotting).
- By adding a large-valued capacitor and a few low-cost components, the power supply can act as a wire-bonder for bonding aluminum wire to objects to be anodized (i.e., Capacitor-Discharge Welding or CDW, also known in some circles as "sput welding").
This device doesn't do anything that a constant-current power supply plus an attentive person with a calculator can't do. But, it will do the ramping, timing, and peak resistance detection autonomously, freeing the operator to do other things.
The hardware components of this power supply are:
- 10-15A, 24-50V fixed or variable voltage switching power supply. A popular brand would be "Mean Well". 24V is likely just sufficient for just anodizing; 48-50V is useful if wire-bonding will be used.
- DPS5015 or DPS5020 Constant-Current/Constant-Voltage buck regulator. Make sure it supports communication (sometimes sold with a USB converter or Bluetooth, though neither adapter is used for this project). The DPS3012 will not work--it does not apparently support ModBus.
- ESP-WROOM-32 module. Make sure the metal shield says "ESP-WROOM-32"--other versions may not work with this code.
- JST-GH 1.25mm 4-pin female cable
- If CDW is desired, a large value (i.e., 0.1 F or more) electrolytic capacitor rated at least 5-10V more than the maximum power supply output, plus a dual relay module.
- Wire, Mini-PV connectors ("DuPont"), AC power switch, circuit breaker, enclosure, fan, fan filters, banana connectors, etc.
The hardware is in a good state. The software is usable, but needs improvement.
Warning: This process involves powerful chemicals, high voltage, and the discharge of very high current. It is critical to use all appropriate safety measures when using this device and process. The author is not a professional anodizer and may be unaware of other hazards. Consult a professional before using. Any use is at your own risk.
See the project wiki for more details: https://github.com/dalegrover/ESSAPS/wiki