Smart Cash Handling Kiosk Development

We are developing a self-service kiosk dedicated to safe, accurate and reliable cash handling. The scope of this project is strictly machine development, electronics, embedded firmware and mechanical engineering. We do not want to use Raspberry Pi, ESP32, Arduino, an embedded PC or similar development-board solutions as the main controller.

The objective is to design and develop our own complete machine architecture, including a custom controller PCB, embedded firmware, cash-handling mechanisms, sensors, actuators, power electronics and mechanical enclosure.

Core Workflow
The machine will allow a customer to:

Insert banknotes and coins.
Detect and identify every deposited cash item.
Maintain and display the running deposited amount.
Compare the deposited amount with the required bill amount.
Once the required amount is reached, retain the exact required amount.
Automatically return any excess amount as change.
Verify that the correct change has been dispensed.
Complete and record the transaction with a full audit trail.
Main Machine Requirements
The machine should include, as applicable:

Banknote validator/acceptor
Banknote escrow mechanism
Banknote stacker or secure storage
Coin acceptor
Coin escrow mechanism
Coin hoppers/recyclers for change dispensing
Banknote recycling/change mechanism where required
Secure cash vault/cashbox
Optical and position sensors
Hopper full/empty sensors
Jam detection
Door/tamper detection
Motor and solenoid control
Custom power supply and protection circuitry
Custom main controller PCB
Service/maintenance interface
Display/user-interface hardware as required
Proven commercial cash-handling devices may be used where appropriate, but they must be integrated into our own controller architecture. MDB, ccTalk, RS-232, RS-485, CAN or other suitable industrial interfaces may be considered depending on the selected devices.

Custom Controller
The project must include the design of a dedicated controller board for the machine.

The controller should be based on a proven industrial microcontroller rather than Raspberry Pi, ESP32 or another general-purpose development platform.

The custom controller should provide:

Real-time control of all cash-handling devices
Sensor monitoring
Motor/solenoid control
Hardware watchdog
Brownout/power-failure protection
Non-volatile transaction/event storage
Real-time clock
Fault and alarm handling
Secure transaction state management
Communication interfaces required by the cash devices
Service/diagnostic interface
Expansion capability for future hardware
The controller should remain capable of safely managing a transaction even if an external display, communication interface or other non-critical component fails.

Transaction Control
The firmware should implement a robust transaction state machine such as:

IDLE → ACCEPTING CASH → ESCROW → AMOUNT REACHED → CALCULATE CHANGE → DISPENSE CHANGE → VERIFY → COMMIT TRANSACTION → COMPLETE

The system must safely handle:

Underpayment
Exact payment
Overpayment
Invalid notes
Rejected coins
Coin jams
Note jams
Hopper empty conditions
Hopper full conditions
Sensor faults
Door opening
Power interruption
Communication failure with a cash device
Incomplete dispensing
Recovery after restart
The system must never mark a transaction as completed until the physical cash movement has been verified.

Change Dispensing
The change-return mechanism is a critical part of the machine.

The controller should calculate the required change and determine the appropriate combination of available denominations.

The system should:

Track the inventory of every denomination.
Select an appropriate dispensing combination.
Detect each successfully dispensed item.
Detect failed dispensing, jams and empty hoppers.
Recalculate or safely abort when the required change cannot be dispensed.
Verify the final dispensed amount.
Prevent incorrect completion of a transaction.
The design should support future expansion to additional denominations where practical.

Mechanical Engineering
The project must include complete mechanical engineering of the cash-handling system.

This includes:

Banknote insertion and transport path
Coin insertion and transport path
Escrow mechanisms
Hopper mounting
Cashbox/vault
Motors and actuators
Sensor mounting
Anti-jam mechanisms
Anti-fishing and anti-tamper mechanisms
Service access
Locking mechanisms
Internal cable routing
Thermal and ventilation considerations
Complete kiosk enclosure
The design should make cash-handling components accessible for maintenance and replacement without requiring unnecessary disassembly of the entire machine.

Electrical Engineering
The electrical design should include:

AC/DC power architecture
Appropriate voltage rails
Over-current protection
Short-circuit protection
Fuse/protection strategy
Motor and solenoid drivers
Sensor interfaces
Isolated communication interfaces where required
EMI/EMC considerations
Grounding strategy
Power-loss detection
Emergency/service isolation
Connector and wiring specifications
Separate power domains should be considered for high-current motors/solenoids and sensitive digital electronics.

Firmware
The project includes the embedded firmware required to operate the complete machine.

Firmware should provide:

Cash-device communication
Sensor monitoring
Actuator control
Transaction management
Cash counting
Change calculation
Change dispensing
Fault detection
Jam detection
Power-loss recovery
Transaction logging
Device health monitoring
Maintenance/diagnostic functions
Error codes and service information
Firmware should preferably be written in C/C++ or another appropriate embedded language suitable for a production industrial controller.

Audit and Transaction Records
Every transaction should generate a detailed record containing, where applicable:

Transaction ID
Date/time
Individual denominations accepted
Total amount deposited
Required amount
Amount retained
Change amount
Individual denominations dispensed
Device status
Errors/faults
Jam events
Transaction completion status
The controller should maintain sufficient non-volatile records to recover safely from unexpected power interruption.

Testing and Validation
The prototype must undergo systematic testing of:

Individual note acceptance
Individual coin acceptance
Multiple-denomination deposits
Exact payment
Underpayment
Overpayment
Change dispensing
Empty hopper conditions
Full hopper conditions
Jam conditions
Sensor failures
Communication failures
Power interruption during transaction
Repeated transactions
Long-duration operation
Cash reconciliation
The target is 99.8% or better cash-item recognition/counting accuracy, subject to clearly defined test conditions and statistically meaningful testing.

Deposits must reconcile precisely with the machine's internal transaction records.

Change dispensing should meet the agreed denomination and quantity tolerance, with physical sensors confirming successful dispensing.

Prototype Deliverables
The expected deliverables are:

Complete system architecture
Cash-handling component selection
Component BOM with manufacturer and sourcing information
Interface specifications for all cash devices
Electrical schematics
Custom controller PCB design
PCB fabrication files
PCB assembly documentation
Mechanical CAD drawings
Complete cash-path design
Enclosure and vault design
Wiring diagrams
Embedded firmware
Transaction and change-control logic
Diagnostic and service functionality
Prototype machine assembly
Functional testing report
Reliability/endurance testing report
Installation and maintenance documentation
Manufacturing documentation for future production
Important Scope Clarification
This is not a Raspberry Pi/ESP32 integration project.

We are looking for a team/company capable of developing the actual machine from the hardware level, including:

Mechanical design + custom electronics + custom controller PCB + embedded firmware + cash-handling integration + sensors + actuators + testing.

A proven industrial microcontroller may be used as the processing core, but the controller electronics and firmware should be designed specifically for this machine.

General-purpose Raspberry Pi, ESP32, Arduino or similar development boards should not be used as the final production controller.

We are primarily interested in engineers/companies with hands-on experience in cash-handling machines, payment terminals, vending machines, kiosks, bill validators, coin acceptors, hoppers, escrow mechanisms, industrial embedded systems and electromechanical product development.

Please provide details of similar machines or payment/cash-handling equipment you have developed, your proposed controller and cash-handling architecture, recommended components, prototype development timeline, testing approach and estimated development cost.