Shared Projects by Eric

Description: This project is adapted from the preliminary design for the “AEC 9005-110-X Low Volts Monitor Module” by Robert L. Nuckolls III. The board simply monitors the connected bus voltage and provides a 1Hz flashing output to drive a warning LED in the event the monitored bus goes below 13V.

This project is intended for use in Experimental category aircraft only. Do NOT install it in a CAR Part 3 or FAR Part 23 certificated aircraft without FAA Field Approval.

BOM: Cost is ~$8 for the components to populate this board. Click for a Digi-Key saved list with those parts.

Download: Click here for a .ZIP archive containing full documentation in PDF format, DipTrace v5.1.0.3 CAD files and RS-274X Gerber files.

Description: This board is as adaptation of the “OVM-14 Mk III Overvoltage Protection Module” designed by Robert L. Nuckolls III, as posted to the AeroElectric-List forum. The board provides overvoltage protection for the charging system in an Experimental category aircraft. It’s a relay driver instead of a crowbar; it opens relay(s) to interrupt the alternator field supply or the AC feed from a permanent magnet stator. It adds several features that are absent in the original version:

1. EFIS alarm output. Sends a 10V (3mA limited) signal to an EFIS alarm input to notify the pilot that the module has tripped.
2. Flashing OVP TRIP indicator LED output. 1.5Hz (20mA limited) output to flash an indicator LED on the instrument panel.
3. PUSH ISOLATE switch. Allows pilot control of a permanent magnet stator feed (as in a Rotax 9-Series engine installation) and pilot reset of the module in the event of a nuisance trip.

The nominal trip voltages are 16.0V in normal mode and 13.7V in maintenance test mode (both values subject to 1% resistor tolerance). The design is tested and working; see performance on the last two pages of the documentation PDF.

This project is intended for use in Experimental category aircraft only. Do NOT install it in a CAR Part 3 or FAR Part 23 certificated aircraft without FAA Field Approval.

BOM: Cost is ~$13 for the components to populate this board, plus builder’s choice of PUSH ISOLATE switch and indicator LED. Click for a Digi-Key saved list with required and suggested parts.

Download: Click here for a .ZIP archive containing full documentation in PDF format, DipTrace v5.1.0.3 CAD files and RS-274X Gerber files.

UPDATE - 29 May 2025 10:20AM PT: Files at the download link have been updated to correct an error in the values for R3 and R5. The circuit board layout is correct. R3 should be 1.02k and R5 should be 10.2k (these values were swapped in the original documentation). All other components are correct.

Board to adapt TO252-3 transistors to 0.1" pitch through-hole. I used them to replace transistors in a circa-1990 NAD 5000 CD player (Q101-Q109). The original transistors (Qodd: 2SB1237 PNP / Qeven: 2SD1858 NPN) are obsolete Rohm Semiconductor parts and I couldn’t find good replacements in a through-hole package. Instead, I replaced then with onsemi 2SB1215 PNP and 2SD1815 NPN which are parametrically similar, handle more power and are still active and available.

The centers of the three through-holes in this board are spaced 0.158" from the bottom edge of the board for this Sullins right-angle header (holes are purposely tight; wiggle the connector pins and they’ll go through). The large TO252-3 pad (collector) is surrounded by thermal vias and both sides of the board are copper floods connected to the collector. Suggest ordering 2oz copper to maximize heat transfer to the board.

This is a simple board to give left stick priority for elevator trim activation in Experimental category light aircraft.

This PCB fits between the solder cups of D-sub connector J1 and is soldered to the connector’s cups. The assembled module fits inside the connector backshell listed in the bill of materials.

All trim switches must pull this board’s inputs to ground. Both outputs from this board pull to ground. Do not connect the outputs directly to a trim motor; the module is intended to provide “up” and “down” signals to an elevator trim controller such as a TCW Technologies Safety-Trim unit or a relay deck.

Connect +12V, trim switches and trim controller to this module using a female 9-pin D-Sub receptacle and appropriate sockets. If a center trim switch is not installed, do not populate pins 3 and 7 of the mating receptacle (the center trim switch is provisioned to accommodate aircraft like the Kitfox, which is designed to have a single trim rocker switch on the center console; adding stick switches results in three sets of switch contacts).

This project is intended for use in Experimental category aircraft only. Do NOT install it in a CAR Part 3 or FAR Part 23 certificated aircraft without FAA Field Approval.

SCHEMATIC & WIRING DIAGRAM: Download here.

BILL OF MATERIALS (Digi-Key): https://www.digikey.com/en/mylists/list/MWE6AGTBZJ

Description: This board is for the “OVM-14 Mk III” Overvoltage Protection Module designed by Robert L. Nuckolls III, as posted to the AeroElectric-List forum. There have been minor changes made to this version, as detailed in the project documentation (see below).

This board provides overvoltage protection for the charging system in an Experimental category aircraft. It’s a “crowbar” type circuit, which is intended to blow a fuse or circuit breaker in the alternator field supply or to open a relay in the AC feed from a permanent magnet stator.

The nominal trip voltages are 16.0V in normal mode and 13.7V in maintenance test mode (both values subject to 1% resistor tolerance). The design is tested and working; see performance on the last page of the documentation PDF.

This project is intended for use in Experimental category aircraft only. Do NOT install it in a CAR Part 3 or FAR Part 23 certificated aircraft without FAA Field Approval.

BOM: Cost is ~$14 for the components to populate this board. Click for a Digi-Key saved list with those parts.

Download: Click here for a .ZIP archive containing full documentation in PDF format, DipTrace v5.1.0.3 CAD files and RS-274X Gerber files.