help customize "slow turn-on" duration in this circuit (link to schematics inside)

jarthel · 15th August 2006, 02:54 PM

http://img112.imageshack.us/my.php?i...titled3bf7.gif

that circuit was found in the datasheet of National's LM150. it doesn't say anything about customizing the duration of the slow turn-on.

also can I also place a 10uF (after the 2nd 1N4002) from Vout to ground?

thanks for the help.

ps. I have just read a similar thread and there were a lot of off-topic replies. please do it somewhere else.

davidallancole · 15th August 2006, 03:28 PM

Changing C1 or R3 would change the turn on time.

You could probably put a 10 uF at the output.

pinkmouse · 15th August 2006, 04:12 PM

Yup, C1 and R3 look like the time delay to me as well. What will you be using this for?

jarthel · 15th August 2006, 10:36 PM

it's for tube heaters.

2 questions:

1. increasing r3 also increases the delay?

2. how about c1?

thank you for the help

infinia · 16th August 2006, 12:08 AM

Hi
R3 and C1 is tau or the time constant. The pnp is clamped on at turn-on so Vout is initially equal to Vref. The output slowly rises to the set output voltage after 3-4 time constants.

50K*100u= 5sec
so output goes from Vref to Vout in about 15-20sec

<edit>
This circuit is a good idea for heater warm up time and to prevent the Vreg from current limiting on start up.

pinkmouse · 16th August 2006, 12:11 AM

I'd breadboard this up, and have a play with different values for R3 and C1. The maths is good to know, as Infinia points out, but the hands on approach is more fun, (for me, anyway).

infinia · 16th August 2006, 12:26 AM

changed c1 to 10uF

jarthel · 16th August 2006, 12:47 AM

can I use this: http://www.ortodoxism.ro/datasheets/toshiba/905.pdf

as the transistor in the circuit? just asking cause I already have it.

ps. to infinia: just sent you an email in regards to spice simulations. thanks again

jarthel · 16th August 2006, 02:47 AM

how about this one? http://www.jaycar.com.au/products_uploaded/PN200.pdf

Thank you for the help

infinia · 16th August 2006, 03:45 AM

Either or will do, not critical only as a switch during turn on/off.

15th August 2006, 02:54 PM	#1
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	help customize "slow turn-on" duration in this circuit (link to schematics inside) http://img112.imageshack.us/my.php?i...titled3bf7.gif that circuit was found in the datasheet of National's LM150. it doesn't say anything about customizing the duration of the slow turn-on. also can I also place a 10uF (after the 2nd 1N4002) from Vout to ground? thanks for the help. ps. I have just read a similar thread and there were a lot of off-topic replies. please do it somewhere else.

15th August 2006, 04:12 PM	#3
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Yup, C1 and R3 look like the time delay to me as well. What will you be using this for? __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

16th August 2006, 12:08 AM	#5
infinia diyAudio Member Join Date: May 2005 Location: Californication	Hi R3 and C1 is tau or the time constant. The pnp is clamped on at turn-on so Vout is initially equal to Vref. The output slowly rises to the set output voltage after 3-4 time constants. 50K*100u= 5sec so output goes from Vref to Vout in about 15-20sec <edit> This circuit is a good idea for heater warm up time and to prevent the Vreg from current limiting on start up. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

16th August 2006, 12:11 AM	#6
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	I'd breadboard this up, and have a play with different values for R3 and C1. The maths is good to know, as Infinia points out, but the hands on approach is more fun, (for me, anyway). __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

16th August 2006, 03:45 AM	#10
infinia diyAudio Member Join Date: May 2005 Location: Californication	Either or will do, not critical only as a switch during turn on/off. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust


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15th August 2006, 03:28 PM	#2
davidallancole diyAudio Member Join Date: Nov 2005	Changing C1 or R3 would change the turn on time. You could probably put a 10 uF at the output.

15th August 2006, 10:36 PM	#4
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	it's for tube heaters. 2 questions: 1. increasing r3 also increases the delay? 2. how about c1? thank you for the help

16th August 2006, 12:47 AM	#8
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	can I use this: http://www.ortodoxism.ro/datasheets/toshiba/905.pdf as the transistor in the circuit? just asking cause I already have it. ps. to infinia: just sent you an email in regards to spice simulations. thanks again

16th August 2006, 02:47 AM	#9
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	how about this one? http://www.jaycar.com.au/products_uploaded/PN200.pdf Thank you for the help

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