Turning Charlize on softly

neil_kaye · 9th March 2006, 02:14 PM

I have just completed a SMPS power supply provided by NUUK at decibel dungeon. I added a three way swithc at the +ve pole a described on DIY paradises's website. When i measure the voltage at postion 1 (270ohm 1/2w resitor) and at postion 2 (no resitor) the voltage is exactly the same. Why is this? I thought that adding the resitor was supposed to provide for a trickle current but i am getting a full blown 12.4 volts?

neil_kaye · 9th March 2006, 03:13 PM

correction it is a 240 ohm 1/2w resitor. Should i try a higher resitance or is it simple an issue of having not connected the amp yet?

Trebla · 9th March 2006, 07:48 PM

Neil.
The resistor should be connected between pin positions 2 & 3 of the switch.
If this is right then you should get a reduced voltage in position 2.
It sounds as though you are taking measurements with your meter before the resistor. Your meter probe should be placed after the resistor ie. on pin 3, even when the switch is in position 2.

Sorry if I have misinterpreted your problem.

D0Hbert · 10th March 2006, 12:20 AM

Need some help, I can't source a 3-step off-on-on switch here, can I use 2pcs off-on switch then put them in series, with the resistor on the "on" position of switch one, while the other end is connected to the "off position" of the 2nd switch? Thus, to prevent the pop, with both switches in their "off" position, I turn on switch 1, followed by switch2. Will this work? Thanks.

neil_kaye · 10th March 2006, 04:19 AM

Trebla,

This makes little or no sense to me. I have the resisotr placed between switches 2 and 3. I tested this by severing the resitor connection and measuring the voltage and it drops to zero.
I then tried placing the 240 ohm 1/2 watt resistor as well as a 200 ohm 1 watt resistor (i had it lying around) and still the meter reads 12.4 volts. I then added a led in series with the 240 ohm and the volatge trop to 10.4 volts. So i am adding resistance in the right region but the 240 ohm resistor on its own lets 12 volts through. Is there a different resistor i should be trying. Right now i am using a 240 ohm metal film resistor.
What should my volt meter be reading with this resistor?

vt4c · 10th March 2006, 05:30 AM

Hi Neil,
If your measurements are taken off from the soldering terminal of the switch, the readings you've seen are correct. All 3 positions will measure the same voltage as the PSU/SMPS.

In order to see the 'soft-start' voltage, the measurements will need to be taken from the soldering terminal at position 3 only (with respect to the negative terminal of the PSU/SMPS); and a load is connected (i.e. - Charlize). When the switch is at :-

1.) Position 1 - No voltage should register on terminal pin 3
2.) Position 2 - About 4V to 6V will be registered on terminal pin 3 (Charlize is connected)
3.) Position 3 - The same voltage from the PSU/SMPS

Hope my explanation helps.

Cheers.

neil_kaye · 10th March 2006, 10:28 PM

thanks vt4c... i thought i was going crazy

eVITAERC · 12th March 2006, 04:46 PM

Yes there has to be some external load for this to work correctly. For more information, please see Ohm's Law

9th March 2006, 02:14 PM	#1
neil_kaye diyAudio Member Join Date: Dec 2005 Location: San Francisco	Turning Charlize on softly I have just completed a SMPS power supply provided by NUUK at decibel dungeon. I added a three way swithc at the +ve pole a described on DIY paradises's website. When i measure the voltage at postion 1 (270ohm 1/2w resitor) and at postion 2 (no resitor) the voltage is exactly the same. Why is this? I thought that adding the resitor was supposed to provide for a trickle current but i am getting a full blown 12.4 volts?

10th March 2006, 05:30 AM	#6
vt4c diyAudio Member Join Date: Jan 2001 Location: Malaysia	Re: Turning Charlize on softly Hi Neil, If your measurements are taken off from the soldering terminal of the switch, the readings you've seen are correct. All 3 positions will measure the same voltage as the PSU/SMPS. In order to see the 'soft-start' voltage, the measurements will need to be taken from the soldering terminal at position 3 only (with respect to the negative terminal of the PSU/SMPS); and a load is connected (i.e. - Charlize). When the switch is at :- 1.) Position 1 - No voltage should register on terminal pin 3 2.) Position 2 - About 4V to 6V will be registered on terminal pin 3 (Charlize is connected) 3.) Position 3 - The same voltage from the PSU/SMPS Hope my explanation helps. Cheers.

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9th March 2006, 03:13 PM	#2
neil_kaye diyAudio Member Join Date: Dec 2005 Location: San Francisco	correction it is a 240 ohm 1/2w resitor. Should i try a higher resitance or is it simple an issue of having not connected the amp yet?

9th March 2006, 07:48 PM	#3
Trebla diyAudio Member Join Date: Nov 2005 Location: North West	Neil. The resistor should be connected between pin positions 2 & 3 of the switch. If this is right then you should get a reduced voltage in position 2. It sounds as though you are taking measurements with your meter before the resistor. Your meter probe should be placed after the resistor ie. on pin 3, even when the switch is in position 2. Sorry if I have misinterpreted your problem.

10th March 2006, 12:20 AM	#4
D0Hbert diyAudio Member Join Date: Sep 2004 Location: Manila	Need some help, I can't source a 3-step off-on-on switch here, can I use 2pcs off-on switch then put them in series, with the resistor on the "on" position of switch one, while the other end is connected to the "off position" of the 2nd switch? Thus, to prevent the pop, with both switches in their "off" position, I turn on switch 1, followed by switch2. Will this work? Thanks.

10th March 2006, 04:19 AM	#5
neil_kaye diyAudio Member Join Date: Dec 2005 Location: San Francisco	Trebla, This makes little or no sense to me. I have the resisotr placed between switches 2 and 3. I tested this by severing the resitor connection and measuring the voltage and it drops to zero. I then tried placing the 240 ohm 1/2 watt resistor as well as a 200 ohm 1 watt resistor (i had it lying around) and still the meter reads 12.4 volts. I then added a led in series with the 240 ohm and the volatge trop to 10.4 volts. So i am adding resistance in the right region but the 240 ohm resistor on its own lets 12 volts through. Is there a different resistor i should be trying. Right now i am using a 240 ohm metal film resistor. What should my volt meter be reading with this resistor?

10th March 2006, 10:28 PM	#7
neil_kaye diyAudio Member Join Date: Dec 2005 Location: San Francisco	thanks vt4c... i thought i was going crazy

12th March 2006, 04:46 PM	#8
eVITAERC diyAudio Member Join Date: Aug 2005	Yes there has to be some external load for this to work correctly. For more information, please see Ohm's Law

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