Lyallbay04 said:
hi,
Setting the required level of hysteresis and the upper/lower voltage limits using 'preferred values' of resistors can be tricky.
Problem is, when you change the Rh [fixed] resistor the Vref point moves, so you adjust the Vref and then the switching limits change...
I have found the easiest way is to calculate an approximate value of Rh and Vref,
then include in the Vref and the upper/lower hysteresis circuit, variable resistors.
The variable can be replaced for fixed resistors after you have determined the required fixed values.
[you measure the resistance values of the variable resistors]
Do you follow.?