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i need a control system with the following guidelines. i need the winner of the bid to keep in mind cost effectiveness in design, build, and component cost.
the main idea is to control 18 solenoid valves by means of 6 RF transmitters.
- power input is from a 12vdc 10 amp psu
- solenoid valves are rated at 12vdc 1.4 amps
- i want to use cost effective FET's or similar to control the valves. (no relays wanted)
- the solenoids produce a lot of heat at 1.4 amps so i would like to PWM control them, they are to be soldered to the pcb for cooling instead of heatsinks
- at any point of given time there will always only be a maximum of 6 valves on at a time
- each 3 valves are grouped to be controlled by a single momentary push button RF transmitter which is detailed below
- each time the button on the transmitter is pressed a valves in the corresponding group will be turn on, so press it once, A turns on, press it again, A turns off and B turns on, press it again and B turns off and C turns on, press it again, C turns off, press it again, A turns on and the cycle continues
- i need the ability to operate multiple of these system in the same room
- 18 2 position terminal blocks for each valve (-/+ for each valve)
- 1 2 position terminal block for the power input
- temperature sensing and output control for a fan. i don't have a fan picked out yet so i need it designed in a generic way. ill probably use some sort of 12 or 5 volt computer case time fan.
- the transmitter is to have to use the following components
- CR2032 coin battery, with a selected battery clip that i have
- SMD push button
- ATTiny24a-ssu for the logic
- maximum of 1" by 1.5" PCB board size
- RFM23B-868-D as the transmitters
- a single RFM23B-868-D as a receiver for the main control board
(i have schematics already, i just need your thoughts or suggestions and pcb layout done)
Firmware and MCU
- a main atmel microcontroller to handle everything, needs to big enough to handle all the input lines for the RF module, and enough output lines for the valves, i don't want to use any shifts, i'm trying to keep the BOM down as much as possible.
- handle decoding the RF inputs and PWM'ing the 18 valve outputs.
- when there is no activity for 2 hours, disable all valve outputs
- if a set temperature is reached, turn the fan output on, if the fan does its job and set internal temperature is reached again then turn the fan output off, if the fan does not do its job and internal set temperature is exceeded then shut down all valve outputs until another set temperature is reached again. this is as a safety procession
- firmware written for the transmitters
- components must be easily obtain from mouser.com with source sustainability in mind
- SMD is not a must nor is through hole, the idea is to just keep the cost down and make it work, but also keeping in mind easy components for easy of assembly
project milestones will based on you supplying me with schematics, pcb layout, firmware and my confirmation in steps that we can discuss
PLEASE READ ALL REQUIREMENTS CAREFULLY, I NEED SOMEONE PROFICIENT AND COMFORTABLE WILL EVERY ASPECT AND FEATURE OF THE PROJECT
if you have any further questions please feel free to ask, however i tried to cover most of the important requirements, other than that im very flexible and open to design and routes to take