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Old 15th January 2013, 03:32 PM   #101
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Hi,
To start the sequence you need to enable Q456 by applying a positive voltage to the base. This will enable Q455 > enable Q454 >Q455 will delay and then Q453 will enable relay 452. If you have a positive voltage at the Q456 then
the emitter will be positive.
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Old 15th January 2013, 03:53 PM   #102
srinath is offline srinath  United States
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Can I do that with a 9v battery - It will just be easier a bit ...
Thanks.
Srinath.
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Old 15th January 2013, 04:30 PM   #103
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I think you can do a test by removing 458 connector and with a 1K resistor momentary jump 4 and 1 and all relays should pickup. If everything it is OKAY.
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Old 15th January 2013, 05:40 PM   #104
nattawa is offline nattawa  Canada
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Quote:
Originally Posted by tauro0221 View Post
Hi,
The problem we were looking for 5 volts at pin 2 it is that for the micro to see a logical one the voltage should be 3 volts or higher. Below 3 it can be a zero. The micro it is the one that enable the relays by sending a signal to enable the relays. I am not sure if for the micro to enable the relay it need pin 2 high. That is why we are looking a 5 at pin.
I would not design a power monitor the way you said.

By the circuit shown in the schematic Pin2 is supposed to have a saw-tooth wave form with a flat top at 5V, and a bottom can be as low as near 1V. I don't know what circuit in the micro board looks like, but if I was the designer i'd feed this wave form into an NPN transistor inverter's base, when the mains power is good, this transistor always saturates and outputs a logic 0.

C465 is charged to 5V by the positive cycle of AC, and is discharged by R454 between charge cycles. The time constant of C465*R454 makes sure as few as one missing charge cycle will cause C465 be dicharged to below the threshold of the NPN transistor inverter, causing a logic "1" at its out put. This is supposed to be a very reliable power failure detector and it has a maximum response time of 16.7 mS.

Last edited by nattawa; 15th January 2013 at 05:47 PM.
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Old 15th January 2013, 06:00 PM   #105
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Hi,
What you said it is true but I am looking in the way the micro see a logic zero or a one to determine the status of the signal. There is two way a micro can read the signal logically or analog. If the micro has an A/D it will read like you said because you can set setting from 0 to 5. Now logically it is different. To read zero it is between .5 and 2.75 high it is from 3.75 to 5 volts. How method they are using that it is the question to solve. Logically 2.78 can be a zero or 1. Analog no problem.
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Old 15th January 2013, 06:31 PM   #106
nattawa is offline nattawa  Canada
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Quote:
Originally Posted by tauro0221 View Post
Hi,
What you said it is true but I am looking in the way the micro see a logic zero or a one to determine the status of the signal. There is two way a micro can read the signal logically or analog. If the micro has an A/D it will read like you said because you can set setting from 0 to 5. Now logically it is different. To read zero it is between .5 and 2.75 high it is from 3.75 to 5 volts. How method they are using that it is the question to solve. Logically 2.78 can be a zero or 1. Analog no problem.
My circuit does not need an A/D. The inverter outputs logic levels.


2.78VDC is just an average of that sawtooth waveform shown on a multimeter when one choose to measure with. It tells very little by itself if not nothing. And I'm quite sure an engineer will not feed a sawtooth into an A/D in a consumer electronics micro for a purpose of power failure detection in a real world. There are so many other ways to do it, far simpler and far more reliable and straight forward. An NPN transistor inverter following pin2 is a good example that reliably and quickly provides a logic 0/1 when AC power is good/failure.



Srinath, can you post the schematic showing the circuit around the micro, on the other side of CP458? it should give a bigger picture and help understand the operation of the power board and its controls.
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Old 15th January 2013, 06:51 PM   #107
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Hi,
I agreed 100% with you but remember some time companies short cut to save in cost. Normally I will use what you just described. A simple transistor will give a cleaner signal but it will cost a transistor.
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Old 15th January 2013, 09:00 PM   #108
srinath is offline srinath  United States
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I'll post the schematic - It may take a bit, I am on my son's laptop, and the schematic is on my laptop, which is currently dead.
Just gimme a day or 2. Thanks you 2, I was so glad 1 person was looking at this problem ... now 2 ... thanks.

Cool.
Srinath.
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Old 12th June 2013, 09:29 PM   #109
srinath is offline srinath  United States
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Finally getting back to this - life gets in the way, then you forget.
Anyway I had pretty much traced the problem to a bad soft start board transformer.

T451 in this diagram. The secondary tested like a capacitor, showing a resistance and promptly flipping to open.

Can I get a generic soft start board off ebay ? Or get one of those and pull the transformer off it.

Or a small transformer -

Thanks.
Srinath.
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Old 12th June 2013, 10:04 PM   #110
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Hi,
Check this power transformer in Mouser. Mouser part number 838-3FS-516.
See if the pins are compatible with your board. The transformer it is 16 volts and .800 amps. The relays are 12 volts dc. I think you can use this transformer with no problem or if you have space you can buy one with leads and solder the wires in the boards eyelets for the transformer.
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