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Old 9th July 2008, 05:16 AM   #1
Buzzy is offline Buzzy  Singapore
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Default Question on uPC1237

I would like to build a dc protection circuit for speaker using upc 1237.

However I don't really understand the datasheet. Is it possible i do not connect anything to pin 4 of the upc 1237 and still get it to work ?

Can the capacitors used be DC type and resistors be of 0.5W type ?

Thankz.
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Old 9th July 2008, 07:25 AM   #2
Corax is offline Corax  Germany
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Hi Buzzy,

it's not so hard to interpret the datasheet.

According to the explanation of the function of pin 4 on page 5 of the datasheet (and the table on page 2) you have to apply at least a voltage of (typ.) 0.74V to let pin 6, the output, pull the load (the relay) to ground potential - connecting the speaker to the amplifier.

The power consumption of R4 will only be one-tenth of a Watt at 60Vrms connected to the diode (see figure 2 of datasheet), so a standard 1/4W resistor will do the job.
No need for 0.5W types at all.

The capacitor connected to pin 2 should be an electrolytic with at least 16V, therefore the reverse voltage of max. -0.23V (see table on page 2 of datasheet) won't harm at all.

For the capacitor on pin 4 a 12V electrolytic should be sufficient.

Good luck.
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Old 9th July 2008, 08:30 AM   #3
Nordic is offline Nordic  South Africa
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The only resistor that may be over 1/4W is the one setting the max current for the relay....

Follow the link below my post... you will see a protection module on there.. you can follow that link to a page that even has a table for selecting the correct resistors...
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Old 24th July 2008, 07:12 AM   #4
Buzzy is offline Buzzy  Singapore
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I have built the UPC1237 circuit. How do i test if the circuit is working ? The +Vcc is 62.5V would this be a problem ?
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Old 24th July 2008, 08:09 AM   #5
Corax is offline Corax  Germany
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If you keep the voltages at pin 7 and 8 at a maximum of 8V I guess you can go as far as you want since there is no direct connection to Vcc. Nevertheless the datasheet states that the maximum Vcc would be +60V. Everything above is at your own risk.

My advise would be to split the 15k resistor, i.e. into 7k5 + 7k5 and attach from the 'center' tap a zener (for instance a 36V zener) to GND to limit the Vcc to the chip.
Care should be also taken when using more than 60V as supply voltage for the relay and therefore to the output at pin 6. Either you use a seperate (and lower) relay voltage or you have to add an additional zener diode and series resistor to limit the voltage to the maximum of 60V when the output is inactive. If the power consumption for the diode is too much you might have to use a series transistor in addition.
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Old 24th July 2008, 12:33 PM   #6
Nordic is offline Nordic  South Africa
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Quote:
Originally posted by Buzzy
I have built the UPC1237 circuit. How do i test if the circuit is working ? The +Vcc is 62.5V would this be a problem ?

On power on with no source connected to the module, there should be a short delay, then the relay should click... (As there is no source, there is no DC on the input pin.) An easy way to test if it blocks DC is to repeat but this time with an AA batery connected to the input, NO speaker on the output until the very end please...
The DC should be enough to prevent the relay from clicking on this time...

Please wear protective eyewear, I once shorted the bottom of the PCB (didn't cut leads short enough). It blew out a chip from the midle of the IC... with those high voltages I guess this is always a likelyhood.
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Old 30th July 2008, 05:41 PM   #7
Buzzy is offline Buzzy  Singapore
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Without signal going to the upc1237 the relay should be open right ? So should I connect the amp to the upc1237 to feed it some signal and at the same time i apply dc voltage to see if the relay opens ? Will i ruin my amp this way ?

The resetting is done using the latching function of the upc1237.

I have connected the relay as normally closed. The amp is always connected to speaker.

Thankz.
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Old 30th July 2008, 06:26 PM   #8
Nordic is offline Nordic  South Africa
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Quote:
Originally posted by Buzzy

I have connected the relay as normally closed. The amp is always connected to speaker.

Thankz.

Why? this seems to be a counterproductive thing to do...
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Old 2nd August 2008, 04:06 AM   #9
Buzzy is offline Buzzy  Singapore
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I have connected up a battery and it does not switch the relay off. I dunno if i have fried the chip. I mistakenly connected the 240V ac to pin 4. But upon connecting correctly i can still hear the realy clicking but it does not detect DC anymore.

Can i check that pin1 is the left most pin when the chip is held facing me with the words right side up?
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Old 2nd August 2008, 07:04 AM   #10
Nordic is offline Nordic  South Africa
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There is a small dimple/ring on the side of pin 1
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