BAT:servo constant current load
2013/6/19
there is several current load . I want a load meet these feature:
* linear load, like a resistor
* linear current scale
* same current scale under all Voltage
* relatively simple
* widely adapt input voltage
* relatively accuracy
* MOSFET: low voltage can get same max current
* NO PWM: linearity
PWM dummy load
* load linearity: X
* linear scale : X
* same scale : X
* relatively simple : V
* widely input voltage: V
* relatively accuracy: XV (average)
Mirror current dummy load
* load linearity: V
* linear scale : V
* same scale : X (low voltage, low max current )
* relatively simple : V
* widely input voltage: X
Ic1 = Iref*(Re0/Re1)
Iout = Iref*(Re0/Re1) = Iref*{[(Vin-0.6)/Iref]/Re1} = (Vin-0.6) /Re1
Iout * Re1 = Vin - 0.6
suppose 2A is max current, 200R POT of Re1,
Max Re0: 200R
2*Re1 = Vin -0.6
1V get 400mA
0.4*Re1 = 1V-0.6
Re1 = 1 ohm
servo constant current load
* load linearity: V
* linear scale : V
* same scale : V
* relatively simple : X ( need dual internal power supply)
* widely input voltage: V
* relatively accuracy: V
Simple servo constant current load by stevecoates.net
* load linearity: V
* linear scale : X
* same scale : X
* relatively simple : V
* widely input voltage: V
* relatively accuracy: V
My version of dummy load
lm386 version of stevecoates
* from 1V to 15V, 2A max ( can be better)
* simple and accuracy : few mA error
* linearity : scale and the load
schematic
Quick prototype:
The completed version
