Vertical lift: Prototypes #4, 5, 6

(See also prototypes 1 through 3.) Prototype #4: Quad-Pulley Elevator (axled) A fundamental shift in design vis-à-vis prototypes 1-3, lift #4 raises a rectangular platform via four corner pulleys. Design: 1/2" steel pipe structure. Flanges bolted to pulleys for pipe framework attachment. To minimize drive complexity, a single 12V/2000lb winch ($50, Chicago Electric model 92860) draws all four pulleys simultaneously via a pair of axles. Several additional pulleys redirect cable f...

Vertical lift: Prototypes #1, 2, 3

Objective / Constraints Automated vertical transportation. Vertical travel: 100 to 200cm. Load: 4 to 30kg. Some objects must remain at a constant orientation and cannot endure significant acceleration or jerk.  For instance, unenclosed liquids and most LCD displays cannot withstand impacts and must be oriented within a few degrees of vertical at all times. SPOILER: Of 8 prototypes, the first 7 failed in practical applications. Prototype #1: Electric scissor jacks 12VDC/6...

PCB release: Peripheral Driver

First release of PCB design: Peripheral Driver. 2 layers, 1.3x2in (33x50mm). ATmega328 (or similar) microcontroller logic at up to 20MHz clock. Eagle design files and BOM available via GitHub repository: PCB-PeripheralDriver. Each of the 22 three-pin peripheral headers provides low-voltage power, a unique microcontroller signal pin, and a common ground. Intended to manage peripherals with high current requirements and/or noisy electrical feedback: servos, relays, high-lumen lighting, act...

Philips PCD8544 driver v0.2 (beta, first release) and MapOS server

C++ driver for the Philips PCD8544 LCD controller, based on Fandi Gunawan's C driver.  Ported to C++ for object-orientation and template support.  Supports multiple LCD controllers with separate DC/CE/RST pins, screen caches, etc.  Other enhancements include support for any resolution (not just 84 x 48) and templated pin and SPI bus access for easy porting to new architectures.  Code is GPL'd in the GitHub repository Philips_PCD8544_driver. The MDFly model MD8448B boards pictured here pro...

Small-volume PCB costs

Expanding on a summary by Entropic Memes, * DorkbotPDX (any size): $0.26/cm², no min area, but must order 3 boards. * BatchPCB (1in²): $2.7/cm², 6.5cm² min * BatchPCB (3in²): $1.15/cm² * Seeed Studio (5cm side): $0.12/cm², 250cm² min * Seeed Studio (10cm side): $0.10/cm², 500cm² min * OurPCB (20in²): $0.023/cm² (plus shipping), 12900cm² min DorkbotPDX and BatchPCB win the small-volume contest up to about $30 (115cm² from DorkbotPDX or 39cm² from BatchPCB).  DorkboxPDX is certainly the che...

Meanwell S-350-12 12VDC power supply

ATX power supplies, as are found in most PCs and cheaply on eBay, shutdown in the event of a current overload (or short circuit) until the 120VAC input is power cycled (disconnected and reconnected). This is a reasonable response in the context of sensitive motherboard components. However, some AT units (e.g. ATR5) carry large inductive loads (kilowatt DC motors) which instantly kill ATX supplies due to their spin-up current surges. The Meanwell S-350-12 switching power supply resembles a...

High Current DC Connectors

Small diameter barrel connectors (1- to 2-pole, different sizes incompatible) are the ubiquitous low-current DC connector, supplying up to 2A.  USB Mini-B connectors supply only about 1.5A max (plenty for logic!), whereas reliable but bulky Molex connectors (2- to 26-pole) can handle 5A.  SAE 2-pole connectors can handle at least 5A, and are hermaphroditic (which simplifies charging, for instance). Servos often use a 3-pin connector, 26- to 22-gauge, where the third wire is a low-current signal ...