Hi,
Here is my problem. I have a relay output that is driving a valve (0->24VDC). Essentially this is on until reset. I want to replace this with a latching valve driven by an L293 without changing all the other circuitry.
So if I step down the output voltage to 5V how can I get a rising edge to trigger one monostable (i.e. 1, 0 to the L293) and a falling edge to trigger another monostable (i.e 0, 1 to the L293). The pulse lengths need to be about 1 second.
I have been racking my brains about this for a while and have been trying with a negative and positive trigger HEF4047B but it wont work because the on time is too long ( i.e. it is not a pulsed trigger input). I am thinking that a monostable 555 might be the best way but I'm not sure how to do the triggering with a falling edge and combining the two.
If anybody can help I would be grateful.
Here is my problem. I have a relay output that is driving a valve (0->24VDC). Essentially this is on until reset. I want to replace this with a latching valve driven by an L293 without changing all the other circuitry.
So if I step down the output voltage to 5V how can I get a rising edge to trigger one monostable (i.e. 1, 0 to the L293) and a falling edge to trigger another monostable (i.e 0, 1 to the L293). The pulse lengths need to be about 1 second.
I have been racking my brains about this for a while and have been trying with a negative and positive trigger HEF4047B but it wont work because the on time is too long ( i.e. it is not a pulsed trigger input). I am thinking that a monostable 555 might be the best way but I'm not sure how to do the triggering with a falling edge and combining the two.
If anybody can help I would be grateful.