Project Description
We are seeking an experienced US-based electronics designer to design, fabricate, and test a prototype PCB for a safety-critical interlock device. This is a well-specified design project with a clear deliverable: a working prototype board ready for design review.
The Project:
The board is a battery-powered discrete logic safety interlock — no microcontrollers, no firmware, no programmable logic of any kind. All timing, sequencing, and gating must be implemented in fixed-function CMOS ICs (CD4000B series or equivalents). The design must be fully auditable by a competent engineer using only a multimeter and oscilloscope. Key functional elements include:
Multi-condition interlock logic (startup delay, tilt sequence detection, auto-shutoff timer, dual lockout switches, manual activation)
Four-step directional tilt sequence using ball-type tilt switches with RC debouncing
Onboard timing circuits (~10 sec startup delay, ~60 min auto-shutoff)
Continuity test circuit for the user-attached output device
LED status indicators (red/green/blue)
N-channel MOSFET output switch rated ≥1A
Snap/spring-terminal connectors for all external connections
What We're Looking For:
Proven experience with analog/discrete logic circuit design and PCB layout (KiCad or equivalent)
Demonstrated ability to design for low cost at moderate volumes (500–1,000 units) (This contract is specifically for prototyping, not low-to-moderate volume production)
Familiarity with CMOS logic families and timing circuits built from discrete components
Experience with tilt/inertial sensors and debounce design is a plus
Clean, well-documented schematics with labeled test points and logical block organization
Deliverables:
Complete schematic and PCB layout files
BOM with preferred vendors/part numbers
At least one assembled and tested prototype
Brief test report confirming functional requirements are met
US Persons Requirement:
Due to customer requirements, this engagement is open to US Persons only (US Citizens, Lawful Permanent Residents, and equivalent classifications as defined under US export control law). Proof of status will be required prior to contract execution.
If you have designed safety-critical or auditable hardware before, or have experience with all-discrete logic implementations, please highlight that in your proposal along with relevant examples of past work.