We currently sell electric infra red heaters that are suitable for warehouses, workshops etc. These are rated up to 230V 6kW 26A, although it is quite rare to be more than 3kW 13A. Mostly these are wired direct to the electric supply via a big switch with a heavy circuit breaker, but we do have a need for an electronic controller in a separate box between the heater and the electric supply that can do three things:
1. Switch the unit on slowly, like turning a dimmer switch. The point is that the current drawn when the heating lamps are cold is very high - this can blow some circuit breakers if you go to full power straight away. A timescale to get to full power of 3 seconds avoids the peak current.
2. Include a digital thermostat (eg via a thermister). This would save power by switching off the heaters when the room temperature is warm enough. Set point adjustment would be via a control knob. A 3 segment LED display would be provided. Normally the display would show the current room temperature, but if you turn the ajustment knob it would switch to displaying the set point and allow adjustment up or down. When the knob is released the setpoint should continue to be displayed for the next 2 seconds, then the room temperature should be displayed again. There should be a build-in offset factor of (say) 2 degrees so if the heater switches off at say 15 degrees it does not switch back on again until the temperature falls below at least 13 degrees (this avoids rapid switching around setpoint).
3. PIR - we would like to add a motion detector, with an adjustable range selection and an adjustable timer selection. The unit would only come on if motion was detected, and would stay on after that for the timer selection period (up to 10 minutes). Sensitivity and range adjustment would work in the same way as temperature, ie if you adjust the relevant control knob the display will switch to showing the setting for the relevant control until the knob has been released for 2 seconds. Then the display goes back to showing the room temperature.
A red LED next to each knob would come on when the knob was rotated, so that it was clear to the user what adjustment was being made.
Three further LEDS would show if the PIR detection was active, and if the temperature was above set point and if (based on the selection below) the unit is supplying power or not.
4. A mode control switch with 5 settings:
1 controlled by temperature only (ie on if its cold, regardless of people)
2 controlled by motion only (ie on if people present, regardless of temp)
3 controlled by temp and motion (on only if cold AND people present)
4 on (on regardless of temp or people).
If the knob is rotated the display will show the selected mode for 2 seconds (ie 0-4), then revert to the temperature display.
The unit should "remember" the settings so it will restart from last time on power up.
I assume the unit would be implemented via a small microcontroller.
We need to consider the housing that the electronics would go in and would allow the connections to be made. An industrial style is fine.
It might be better for the thermister and PIR to be remote items that connect to the box there are already off the shelf parts that can do what we need.
We probably wont have the resources to test for EMC (radio interference) but we should bear the need to avoid interference during design.
We can discuss whether to rate the unit up to 3kW only, or 4.5kW+. Depends largely on whether higher ratings are harder to do. Likewise single phase only, or three phase.
16 freelancere byder i gennemsnit $594 for dette job
Hello. Ready for this job. I have strong experience in SW and HW design with MCU. I would be glad to work on your project. Price included schematic, PCB desing, specification and MCU programm. Regards.
Hello Dear! I can do this project comfortably within given time as I have 5 years of experience in Microcontroller software/hardware co-design. I am 100% sure that I can deliver what you require. Thanks