DIY Constant-current Rectifier from a Bench Supply
自制恒流整流器：桌面电源加限流方案
标签：自制工具, 恒流源, 限流电阻, 桌面电源, 入门设备
小件电解着色无需千元级工业整流器：一台二手可调直流稳压电源（0–30 V / 5 A，约 150–400 元）串联大功率水泥电阻（2–10 Ω、50 W）即可近似恒流运行，着色小件所需电流常仅 0.05–0.3 A；更进一步用 LM317 三端稳压器加一只取样电阻搭建恒流电路，精度可达 ±2%。自制要点：正负极接线柱采用带护套香蕉插头，槽体旁装 10 A 保险丝，阳极铜排涂绝缘漆防短路。首次通电用废试片验证电压-电流关系并贴标签存档。
Small-part electro-coloring needs no industrial rectifier: a second-hand bench supply (0–30 V / 5 A, 150–400 CNY) with a series power cement resistor (2–10 Ω, 50 W) runs near-constant-current, since coloring draws only 0.05–0.3 A. For tighter control, an LM317 plus one sense resistor forms a constant-current loop within ±2%. Build safely: shrouded banana terminals, a 10 A fuse beside the tank, and insulated anode busbars. First runs use scrap coupons, logging voltage-current pairs on a label.