temperature control unit

[wyn]

hi folks can anyone help me with this project the temperature control unit.i will apreciate it.

The unit has to perform the following
functions:•

The temperature is to be controlled as a function of light intensity. This means that the darker the ambient
light becomes, the more heat is to be generated by a heating element.
• In order to conserve energy, the part of the system that heats up the element must have the highest
possible efficiency.
• A user interface must inform the user of all operational statuses (e.g. indicator for heater element
ON/OFF).
Design constraints:
The following must be implemented in your design:
• To meet the requirement of high efficient heating, the heater element must be supplied with DC-chopping (pwm).
For this a NE555 timer IC must be used.
• The heater element to be used is a 12 VDC lamp (those used in motor vehicles) which provides good
infra red radiation as a heat source.
• The power supply for the system must be a +12 VDC source (battery or mains operated PSU).

The unit should comply to the following specifications:

• Heater element to be controlled: 60 W (connected externally to the unit via banana connectors
and cables).
• Maximum temperature at 3 cm distance from heater: 40 oC
• Operating voltage: 12 VDC.
• Control voltage: Chopped DC voltage.
• Light sensor: LDR or phototransistor.

 

[Reloadron]

Is this a homework or school assignment as the forums have a section dedicated to to just that.

How do you think would be a good way to go about doing this? Do you have a plan, basic circuit?

Ron

 

[wyn]

Hi thanks for the reply .it is a project .my plan is to use the ldr on pin 5 of the 555 timer,for the pwm part .i also attended to use the resistors R1 and R2 and the cap to give me a ratio of 1000hz .the temperature sensor that must be mounted 3cm from the light source must switch off the circuit if it reaches 40 degrees celcuis so i attended to use a sensing circuit with a comparator coupled to pin4 of the 555 timer .when it reach 40 degrees celcuis the temperature sensor will give a output and i wiil take that output to my comparator (sensing circuit) then it will compare and give a output that will stop the 555 timer.the output of the 555timer pin 3 i attended to use a mosfet to drive the light bulb .im not sure how to implement it and is not sure if it is right.

 

[Reloadron]

I would likely think about using a 555 configured in a PWM circuit similar to this or along those lines. For the temperature sensor maybe use a LM35 configured along these lines or a thermistor circuit with a comparator. Maybe use the output of the temperature sensing portion to inhibit the 555 operation with a low when temperature is exceeded.

Just a few thoughts on it. There are likely several other ways to go about it.

Ron