Is this PCB OK for GC?
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 16th October 2008, 12:38 AM #1 samsagaz   diyAudio Member   Join Date: Aug 2004 Location: Argentina Is this PCB OK for GC? Hi guys, i was all the night trying to make an PCB for my new GC. you think that this it good enough?
 16th October 2008, 07:50 AM #2 pacificblue   diyAudio Member   Join Date: May 2008 Did you calculate the power dissipation for all resistors correctly? P=(U^2)/R for the bleeders and P=U*I for the LEDs resistor.
samsagaz
diyAudio Member

Join Date: Aug 2004
Location: Argentina
Quote:
 Originally posted by pacificblue Did you calculate the power dissipation for all resistors correctly? P=(U^2)/R for the bleeders and P=U*I for the LEDs resistor.

i didnt calculate it thanks for the Tip/Fix

Let me try to do it.....

Bleeders
-----------
P=(U^2)/R
P=(37^37)/2000
P=1369/2000 = 0.685W

So i think that needs to use like 2Watts resistors bleeders, right?

Led
-----
P=U*I
P=37*0.02=0.740W

To calculate the resistor value i need to use R = 37V / I right? An resistor like 1,9K will be OK?

Looks like needs to use an 2Watts resistor too

AndrewT
diyAudio Member

Join Date: Jul 2004
Location: Scottish Borders
Quote:
 Originally posted by samsagaz Bleeders ----------- P=(U^2)/R P=(37^37)/2000 P=1369/2000 = 0.685W Led ----- P=U*I P=37*0.02=0.740W To calculate the resistor value i need to use R = 37V / I right? An resistor like 1,9K will be OK?
make the resistor values larger.
Try 4k7 for the bleeder, if you think you need them.
Try 2mA to 5mA for the LED, not 20mA, i.e. 18k to 7k5.
__________________
regards Andrew T.

 16th October 2008, 12:28 PM #5 ratza   diyAudio Member     Join Date: Dec 2007 Location: Sibiu, Romania I use 2.2k bleeders rated at 2W and they're stone cold at 30V. My LED is connected between the positive and the neagative rail and it has a 22k / 0.6W resistor which is also cold. The current through the LED is only 3mA, but the light is very visible. At 15mA it was very annoying. __________________ Any solution is a compromise.
AndrewT
diyAudio Member

Join Date: Jul 2004
Location: Scottish Borders
Quote:
 Originally posted by ratza I use 2.2k bleeders rated at 2W and they're stone cold at 30V.
we would all expect a 2W resistor to be cool when dissipating 400mW!!!
Quote:
 Originally posted by ratza My LED is connected between the positive and the negative rail and it has a 22k / 0.6W resistor which is also cold. The current through the LED is only 3mA, but the light is very visible. At 15mA it was very annoying.
200mW through a 600mW will run warm.

Now he needs to calculate for his chosen values. Guessing is not permitted.
__________________
regards Andrew T.

samsagaz
diyAudio Member

Join Date: Aug 2004
Location: Argentina
Quote:
 Originally posted by AndrewT make the resistor values larger. Try 4k7 for the bleeder, if you think you need them. Try 2mA to 5mA for the LED, not 20mA, i.e. 18k to 7k5.

If i use 4k7 instead 2k, the diference will be that the cap will be discharged at half of time, right? (Will use 4k7)

ok, will change Led Resistor too... 10K is an easy value to find.

 16th October 2008, 01:41 PM #8 samsagaz   diyAudio Member   Join Date: Aug 2004 Location: Argentina Someone know the Pin space of the 2Watts Resistors? im using altium, for 1/4 i was using Axial 0.3, now dont know wich to choice for 2Watts i dont have any 2Watts resistor in stock to check the space, i can choice Axial 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0....
 16th October 2008, 02:01 PM #9 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders calculate the dissipation in the resistors. Adjust the resistor value to ensure the dissipation is <50% of rated maximum. Then you don't need any 2W resistors. __________________ regards Andrew T.
samsagaz
diyAudio Member

Join Date: Aug 2004
Location: Argentina
Quote:
 Originally posted by AndrewT calculate the dissipation in the resistors.Adjust the resistor value to ensure the dissipation is <50% of rated maximum.Then you don't need any 2W resistors.
oh, nice, so for example

if i use 12k for Bleeders, i can use 1/4W resistor. and can use 10K for led and can use 1/4W too, right?

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