Hello,
this is my first regular post. I am novice in electronics.
I am working on a timer relay that will disconnect power to three separate devices for roughly 10 seconds, and activate them again.
http://www.kpsec.freeuk.com/555timer.htm#monostable
I was using that circuit and created the test circuit with R1=33K and C1=220micro. I intend to connect a NC relay on the pin 2 output. Then I intend to connect three separate NC relays in parallel for the three devices (in the circuit where the first relay is the switch).
Then I thought why don't I use stronger power supply for my device and power all three devices from my circuit (instead using their original power regulators and cutting their cables).
Questions:
1. Do I need a diode on exit of NE555 to protect it from the coil in the relay or should I connect the diode across the coil of the relay?
2. I have three devices using factory power supplies 9V@1.5A, 5V@1A and 7.5V@1.5A. If I use voltage stabilizers with nominal current of 1.5A (TO220), is it enough current for my devices? (I intent to use 7809, 7805 and LM350 for 7.5V)
3. Is 12V@5A power supply enough for all devices, assuming that relays will not be energized at the same time when the devices. In devices mode I calculated 4.1A consumption and in reset state I assumed roughly 250mA for relays and a few hundred mA for the NE555. Is 20% margin enough?
4. Do I need any fuses anywhere in the circuit?
5. If I would want an signaling LED, where shall I put it? I would not want to add more load to the NE555 output, but in the second circuit behind the first relay I can add a LED with appropriate resistor, right?
Thank you all for your input, it will be much appreciated
SaleB
this is my first regular post. I am novice in electronics.
I am working on a timer relay that will disconnect power to three separate devices for roughly 10 seconds, and activate them again.
http://www.kpsec.freeuk.com/555timer.htm#monostable
I was using that circuit and created the test circuit with R1=33K and C1=220micro. I intend to connect a NC relay on the pin 2 output. Then I intend to connect three separate NC relays in parallel for the three devices (in the circuit where the first relay is the switch).
Then I thought why don't I use stronger power supply for my device and power all three devices from my circuit (instead using their original power regulators and cutting their cables).
Questions:
1. Do I need a diode on exit of NE555 to protect it from the coil in the relay or should I connect the diode across the coil of the relay?
2. I have three devices using factory power supplies 9V@1.5A, 5V@1A and 7.5V@1.5A. If I use voltage stabilizers with nominal current of 1.5A (TO220), is it enough current for my devices? (I intent to use 7809, 7805 and LM350 for 7.5V)
3. Is 12V@5A power supply enough for all devices, assuming that relays will not be energized at the same time when the devices. In devices mode I calculated 4.1A consumption and in reset state I assumed roughly 250mA for relays and a few hundred mA for the NE555. Is 20% margin enough?
4. Do I need any fuses anywhere in the circuit?
5. If I would want an signaling LED, where shall I put it? I would not want to add more load to the NE555 output, but in the second circuit behind the first relay I can add a LED with appropriate resistor, right?
Thank you all for your input, it will be much appreciated
SaleB
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