Hello all,
I am trying to build a circuit that will operate a motor for about 3 seconds, this is via relays. The 556 timer operates the relays to provide power to the motor in either direction, depending on which trigger it recieves. The circuit is currently on proto-board.
Disregarding the motor, as that is a simple case of wiring power to it through the relays, I have an issue with the 556 circuit that drives the relays. The schematic is below...
I've been receiving help but they have now decided they no longer wish to so some of the design is things that have been suggested to me which I'm still not 100% on understanding.
The main issue is the fact that both relays are energising when I trigger just one side of the 556. If I trigger one side, one relay should energise. Trigger the opposite side and the other relay should trigger. It is a BJT 556 as opposed to a CMOS.
Also, of the things suggested I add to the circuit, I understand the purpose of the 10k pull-up resistors but I'm not entirely sure of the purpose of the 1N4148 diodes. It was explained briefly as preventing the trigger pin going higher than Vcc though perhaps someone could explain how that may happen without the diode.
The only other thing is the rating of the fuse. Is it a case of measuring the normal current draw of the circuit and selecting the appropriate fuse or should there be a way to calculate it? Is it even needed or am I being over cautious?
Any help is appreciated! Thanks in advance. If there is any more info that is needed, let me know.
I am trying to build a circuit that will operate a motor for about 3 seconds, this is via relays. The 556 timer operates the relays to provide power to the motor in either direction, depending on which trigger it recieves. The circuit is currently on proto-board.
Disregarding the motor, as that is a simple case of wiring power to it through the relays, I have an issue with the 556 circuit that drives the relays. The schematic is below...
I've been receiving help but they have now decided they no longer wish to so some of the design is things that have been suggested to me which I'm still not 100% on understanding.
The main issue is the fact that both relays are energising when I trigger just one side of the 556. If I trigger one side, one relay should energise. Trigger the opposite side and the other relay should trigger. It is a BJT 556 as opposed to a CMOS.
Also, of the things suggested I add to the circuit, I understand the purpose of the 10k pull-up resistors but I'm not entirely sure of the purpose of the 1N4148 diodes. It was explained briefly as preventing the trigger pin going higher than Vcc though perhaps someone could explain how that may happen without the diode.
The only other thing is the rating of the fuse. Is it a case of measuring the normal current draw of the circuit and selecting the appropriate fuse or should there be a way to calculate it? Is it even needed or am I being over cautious?
Any help is appreciated! Thanks in advance. If there is any more info that is needed, let me know.