Post on 27-Jul-2015
Sometimes we want to design a controller for a panel heater
PWM?
Designing the circuit with analog components would be difficult.
Continuous voltage control?
The power dissipation would not be acceptable.
Sigma delta?
You may not know how to design it.
But it is easy to implement at very low cost.
You may not know how to calculate the value of the components, but can find the appropriate values with simulations.
The circuit
V2
5
GND
TRIG
OUT
RST CV
THRS
DIS
VCC
U3
TLC555
R81meg
C5
1u
R11
100k
R12
1megC1
1u
R2
100k
V1
SINE(0 2.5 0.02)
U4
C3
0.01u
R110k
R310k
C4
0.1u
U2U5R4
10k
R5
10k
R6
1 C2
0.1u
C6
0.1u
VDD
VDD
SDOUT
VCON
VC
VDD
V2
VFB
VFB
VDD
VDD
HVDD
HVDD
2
HVDD VD
D
VDD
HVDD
2
HVDD
2
BVCVI
.tran 1000
.IC V(SDOUT)=2.5
.ic V(VC)=2.5
*.options cshunt=1e-15*.options gshunt=1e-9
.include ./NJM2902OPAMP/njm2902_2.lib
A sigma-delta implementation with a TLC555
Output filter
SDOUT is a smoothed voltage of the ADC output.
LM2902LM2902
Z of PS
Bypass caps
LM2902
Features:Low costFor relatively slow signals
Performance
0s 10s 20s 30s 40s 50s 60s 70s 80s 90s 100s0.0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V0.0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V-0.5V
0.0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V
V(vfb)
V(sdout)
V(vi)
Input waveform
SDOUT, smoothed output waveform
Sigma-delta ADC output waveform
Frequency domain waveform of SDOUT
Conclusion
You can control a panel heater with a solid state relay connected to a sigma-delta ADC. The VFB signal can be used to control the solid state relay.
You can apply an analog voltage, which can be set with a variable resistor, on the ADC’s input to control the power of the panel heater.
Hoping that you will have good luck with your home project!
If you want the data deck of the circuit, send a request to yamaken@erqii.com