LM1458 ic operation connected to a light dependant resistor (LDR)

[McPlay]

hello
i am controlling the direction of a dc motor via an Hbridge. i am using the outputs of the dual LM1458 comparator IC to do this. i have LDRs at my LM1458 inputs. what is the relationship between the state of the LDRs and the output of the LM1448 dual comparator? how does this comparator work exactly?

 

[mister_rf]

It’s more efficient to share the schematics… is this the diagram you are talking about?

**broken link removed**

---------- Post added at 01:45 ---------- Previous post was at 00:42 ----------

This is a window comparator circuit that employs a dual op-amp IC, the 1458 and some LDR on the inputs. The LDR (or Light Dependent Resistor) is a simple component that provides a variable resistance that changes with light. If both LDR's see the same amount of light, their resistance is equal. In this case the junction of the LDR's would be at input voltage divided by two, for example on 12V input - junction of LDR's at 6V. If the light on one LDR is greater than the other, than the voltage will move, higher or lower depending on which LDR has more light.
This window comparator compares the input signal fed by the junction of the LDR's, to a 'low' and a 'high' reference voltage level (let’s consider VRef Low and VRef High, respectively), and outputs a logic low level if it falls between these two reference levels. The limits are set by the resistors in series from +V to 0V, and adjusted by the two trim pots. One of the op amps is used for comparing the input to VRef High while the other op amp is used for comparison with VRef Low. If the input is higher than VRef High or lower than VRef Low, the output goes to logic high.
Each comparator output control a pair of NPN/PNP bipolar transistors . In the current configuration if a high level voltage is applied to the pair of NPN/PNP transistors, only the NPN start to conduct the current and the PNP transistor remain blocked. If we apply a low level voltage then situation change, now the PNP start conducting and the NPN remain blocked.
The two pairs of transistors are connected in a H-bridge. (Left side NPN/PNP transistors and right side NPN/PNP transistors)
An H-bridge enables DC electric motors to be run forwards or backwards.
The basic operating mode of an H-bridge is fairly simple: if left side PNP and right side NPN are turned on, the left lead of the motor will be connected to ground, while the right lead is connected to the power supply. Current starts flowing through the motor which energizes the motor in (let’s say) the forward direction and the motor shaft starts spinning. If we change and turned on the right side PNP and left side NPN transistors, the converse will happen, the motor gets energized in the reverse direction, and the shaft will start spinning in that way.

The bottom line, if light change, the LDRs change value and the voltage moves outside these limits, then the respective op-amp will activate the motor and move the system appropriately.