Hi Folks, can someone advise the best way to deal with this. This is a switching circuit for an intermittent wiper delay system - a little complex but I want to use the original switch without adding anything that shouldn't be there. The switch on the diagram is part of the complex original switch that I have to use so I'm stuck with it. This is the theory - S1 (normally closed to earth) is opened and closed (springs back to closed). This activates monostable that sets pin 1 of the 4001 to low for a few seconds. Wiper switch is then flicked the other way to close S2 that momentarily brings pins 5 and 6 to high, and hence pin 2 to low that makes pin 3 high. This makes the transistors latch on and switches the relay on. This then activates the intermittent delay circuit.
The problem is that it keeps blowing the 4001 - it works ok till I connect the motor, and then after a few operations it stops working. The fault is pin 11 does not go low when S1 is opened and I suspect this may be due to spikes from the motor. Although I have shown the motor in the diagram that is not the whole picture - by means of another relay and more components to the switch the motor is reversed and I guess this compounds the problem of spikes. Arcing at the switch contacts may also add to it.
Is this just a matter of putting a cap across the motor? If so, what size? Or does anyone have a better idea?
The problem is that it keeps blowing the 4001 - it works ok till I connect the motor, and then after a few operations it stops working. The fault is pin 11 does not go low when S1 is opened and I suspect this may be due to spikes from the motor. Although I have shown the motor in the diagram that is not the whole picture - by means of another relay and more components to the switch the motor is reversed and I guess this compounds the problem of spikes. Arcing at the switch contacts may also add to it.
Is this just a matter of putting a cap across the motor? If so, what size? Or does anyone have a better idea?
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