Shared Projects by Eric

Cost: $4.15 for three.

Description: 10x analog sensor signal differential amplifier. Connect ‘IN+’ and ‘IN-’ to analog voltage signal. Connect ‘BUS’ and ‘GND’ to +11-30V DC supply. Connect ‘OUT’ to desired system input. Board is configured to use ¼" quick-connect tabs, but wires can be soldered directly if desired.

Digi-Key shopping cart here. Populate PCB as indicated on silkscreen.

TESTED / WORKING

Cost: $3.85 for three.

Description: This board is part of a USB programming adapter for the surface-mount (8-SOIC) version of the PICAXE 08M2 microcontroller. It’s basically a cheap replacement for the Revolution Education AXE-027 USB programming cable.

This board includes the standard PICAXE programming circuit consisting of 22k series and 10k pull-down resistors on the Serial In pin, as well as a 0.1uF decoupling capacitor for the PICAXE. The PICAXE is held in a zero insertion force (ZIF) socket (see Bill of Materials, below). Desolder the ZIF socket from its carrier board and resolder it to this board.

The six-pin header on this board connects to a generic FTDI FT232RL USB to RS-232 converter module. Search eBay for “FT232RL Module” and look for the red module with a jumper to select between 3.3V and 5V TTL (set the jumper to 5V). Bend the right-angle header pins on this module so they’re straight up from the board, solder this adapter onto the pins (ZIF socket facing up), then cut the pins flush.

Since many of the FT232RL modules sold on eBay use counterfeit chips, FTDI’s EEPROM programming utility, FT_PROG (here) is not a reliable way to invert the TX and RX lines as required to mimic the AXE-027 cable. Instead of relying on the ability to program the chip’s EEPROM, this board simply uses inverters comprised of two 2N7002 N-channel MOSFETs (the SOT-23-3 footprints on the board).

My Windows 10 computer recognized the serial converter module and loaded drivers automatically, but if you need drivers for an earlier version of Windows, Linux or MacOS, the FTDI Virtual COM Port drivers are available here.

Bill of Materials:

• 1 ea. FT232RL USB to RS-232 converter module (on eBay, here)
• 2 ea. 2N7002 N-channel MOSFET (SOT-23-3)
• 1 ea. 0.1uF ceramic capacitor (0603)
• 2 ea. 1k-ohm resistor (0603)
• 1 ea. 10k-ohm resistor (0603)
• 1 ea. 22k-ohm resistor (0603)
• 1 ea. 8-SOIC ZIF socket (on eBay, here)

Cost: $20.60 for three.

Description: This board tests the equivalent series resistance (ESR) of electrolytic capacitors and outputs 1 volt per ohm to a multimeter. The design is tested and working.

BOM cost is ~$13 for just the components to populate the board. Click for a Digi-Key shopping cart with those parts.

For cheaper trimmer potentiometers, click to search eBay for “3296W 1M” and “3296W 5k”, sorted by price.

Notes:

1. R1 and D1 are optional power-on indication; the board will work without them.

2. M1 is not obviously marked for pin 1 location. Place part with its conjoined legs on the left, with the board oriented as shown in the OSHPark rendering above.

Download: Click here for a .ZIP archive containing the schematic, DipTrace v3.0.0.1 CAD files and RS-274X Gerber files.

Cost: $0.80 for three.

Breakout board for 8-SOIC and 8-MSOP packages. Converts these 8-pin SMD components to breadboard-friendly 0.1-inch pitch by 0.3-inch width through-hole format. Pins numbered on both sides for quick reference.

Cost: $0.85 for three.

Description:

Miniature DC-DC boost converter for powering a microcontroller or sensor from battery power. This board will operate from 2.7-4.9V, so you can use two or three AA cells, one lithium cell such as a CR123A, 14520 or 18650, or one lithium-ion rechargeable.

With the feedback resistors specified, output is 5V, and the board can supply about 250mA. At 250mA load the components get warm, but temperatures are well within limits.

Bill of Materials:

• U1: Texas Instruments LMR62014XMF Boost Regulator (SOT-23-5)
• L1: Bourns SRN3015TA-100M 10µH Shielded Inductor (SMD 3mm x 3mm)
• D1: ON Semiconductor MBR0520LT1G 20V 0.5A Schottky Diode (SOD-123)
• C1, C3: Yageo CC0603KRX5R6BB475 4.7µF 10V 10% X7R Ceramic Capacitor (0603)
• C2: Samsung CL10B681KB8NNNC 680pF 50V 10% X7R Ceramic Capacitor (0603)
• R1: Stackpole RMCF0603FT10K2 10.2kΩ 1/10W 1% Resistor (0603)
• R2: Stackpole RMCF0603FT3K32 3.32kΩ 1/10W 1% Resistor (0603)

BoM Cost: $2.97

Notes:

1. Output voltage is set by resistors R1/R2. See the LMR62014XMF datasheet for details on setting other output voltages. Keep in mind that a large change will also require changes in inductor and capacitor values. You can safely change to 3.3V output from two AAs by changing R1 to 1.69kΩ, R2 to 1kΩ and C2 to 1500pF.

2. Output pads are 0.1-inch pitch and will accept standard pin headers. They are spaced 0.445 inch apart, input to output.