Hi
That is true, thats why I have just over 1A, but only to say it can be done. In any case you just want to limit current so that fuse doesn't blow, which can be easily made by NTC, but if I have to have relay too, then I will go for my designs (home use) for what I have now. And there are no special parts...
That is true, thats why I have just over 1A, but only to say it can be done. In any case you just want to limit current so that fuse doesn't blow, which can be easily made by NTC, but if I have to have relay too, then I will go for my designs (home use) for what I have now. And there are no special parts...
Resistors or NTC's that's the question......
I know this is an old post but i will add my 2 cents worth anyways.
I like the idea of using NTC's instead of resistors, since they come up slower and smoother as compared to resistors which provide only some resistance or none, e.g only two discrete states.
However, using resistors has the following advantages:
1. they don't run continuously hot, unless of course the relay fails...
2. resistors handle the case of turn-off / quickly turn-on again.
The second point guarantee's 100% soft-start functionality, assuming point 1 doesn't occur.
NTC's when hot have theoretically no resistance, so if the amp is shut off and on again rather quickly, your get little if any soft-start delay.
However if NTC's are used with a relay then they're not on that long, so they probably wouldn't get that hot.
Maybe you can get the best of both worlds by using relays with NTC's!
Also, if the relay fails for some reason, the NTC takes over and powers up the supply slowly as expected.
Adding an LED to the circuit to indicate this "relay-failed-state" or better "relay-opened-state" would make the circuit even more robust. When powering up, the led would go out as soon as the relay's contacts close.
Cheers,
Chris
I know this is an old post but i will add my 2 cents worth anyways.
I like the idea of using NTC's instead of resistors, since they come up slower and smoother as compared to resistors which provide only some resistance or none, e.g only two discrete states.
However, using resistors has the following advantages:
1. they don't run continuously hot, unless of course the relay fails...
2. resistors handle the case of turn-off / quickly turn-on again.
The second point guarantee's 100% soft-start functionality, assuming point 1 doesn't occur.
NTC's when hot have theoretically no resistance, so if the amp is shut off and on again rather quickly, your get little if any soft-start delay.
However if NTC's are used with a relay then they're not on that long, so they probably wouldn't get that hot.
Maybe you can get the best of both worlds by using relays with NTC's!
Also, if the relay fails for some reason, the NTC takes over and powers up the supply slowly as expected.
Adding an LED to the circuit to indicate this "relay-failed-state" or better "relay-opened-state" would make the circuit even more robust. When powering up, the led would go out as soon as the relay's contacts close.
Cheers,
Chris
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I always recommend that resistance is bypassed when it's job is complete.
If it's a soft start then 200ms is complete.
If it's a slow charge then 10 to 20s is complete.
For slow charge a Power Thermistor is better than a fixed resistor.
That Power Thermistor resistance will go back up again when the slow charge cycle nears completion.
If it's a soft start then 200ms is complete.
If it's a slow charge then 10 to 20s is complete.
For slow charge a Power Thermistor is better than a fixed resistor.
That Power Thermistor resistance will go back up again when the slow charge cycle nears completion.
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