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mvs sarma
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Posts posted by mvs sarma
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Hi Brothers and Ssiters,
WISHING ONE AND ALL A VERY HAPPY AND SUCESSFUL NEW YEAR 2007
WITH REGARDS,
Sarma
[email protected]
0 91 94401 54650 -
Hi A.R.mazaheri ,
Welcome to the fourm,
i hope you appeciate that there is going tobe a power loss in the form ohest of 140Watts by designing a Linear reulator using LM723 form 65 to 45 Volts and a current demand of 7 Amps.
Instead, you may consider Switching power supply to get a better efficiency.
Sarma -
hI,
iS THIS WHAT YOU WANTED IT I UNDERSTOOD PROPERLY?
F= 1.44/((R1+2*R2)*C)
(R1+2*R2)= 1.44/F*C
2*R2={1.44/F*C}-R1
R2=[{1.44/F*C}-R1]/2
Sarma -
Hi Hussainking,
you may try PCB123 software is good infact. it claimed to be free. you can send the file to them and order pcb even. you may google for pcb123
Sarma -
how can i start i only know some theories in electronics how can i relate that to the actual ones with hands on resistor or any other devices!! pls help me
Hi, Don't ask questions -- just follow the advises already offered. if i were to be in you position ( abt me - a 61+ retired telecom engineer, still consider myself a dummy and want to learn a lot ) i would have finished a book or two by now. take any faulty board- afforda multimeter and a soldering kit - may be burn your hand --WARNING -- WITH CAUTION--- you will comeout ina month's time-- as you said already goof at fixing PCs -- just GO AHEAD- don't re think. all the best
Sarma
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Hi Panannto,
You are Welcome, i add a comment- this site for ever SERVES too
it is for youngsters to use it to grow their knowledge and try become practical and purposefull
All the best--
Sarma -
Hi,
when you get a rectified dc, though varrying, the DC content is taken by the ic and the variation is treated as source or supply variation. still the control loop of the ic should give you a regulated o/p for obviously minimal load requirements. -
Hi,
if it is fast varrying, try a votage doubler with germanium diodes like OA79, etc, the output can be clamped by three silicon diodes to fgive you around 3XVf of the diodes. this provided the variation is equal at MIN and MX.
otherwiase try MAX1724. it is said of capable of working from 0.8V. Datasheet at
http://datasheets.maxim-ic.com/en/ds/MAX1722-MAX1724.pdf -
Hi,
In support of audio guru's opinion that you can work with one supply, attaches find a application note URL
http://www.national.com/an/AN/AN-1525.pdf
this will enable you work with single voltage. -
Hi
please elaborate your point-- not able to catch it-- you mean deriiving 12v from usb power supply (5V0 for your use in the circuitry used by u.?
if so you may use any Dc-Dc converter ( for eg., MC 34023A in the boost mode.
with few extra components and convert it to 12v for your use.
Is this what you are trying to ask please!! -
Hi
the CC mode is preset for a known constant current-- hence no need to measure.
if you are able to measure the total crt, you can deduct CC paramter and balance is taken by CV unit. -
Man, to see my nefiew cry is heart breaking. :-\
He cryed alot when i said that i won't do it.
Here is my schematic...
F1 has no value yet because i have to build first and mesure later, i dont think R1 could get that hot but 1W resistor wil be a safe value to work with, the two TIP42 should get enought current to PSP without getting also too hot.
So what you think?
Hi Wuemura ,
Replace the D1 with 3 amp diode-- Go ahead-- try mount the transistors on the body of the poer supply cabinet ( if Metal) and insulate them with TO220 type packing kit. If plastic, try a heat sink of aluminum sheet of adequate thickness if you dont get the type suugested by Audioguru--you may try for 200 mA thro' 7805 by reducing the R1 value to 3.3ohms and 1/2 or 1 watt.
fuse can be at 3amps slow blow as already recommended by GURU
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Hi Audioguru,
Current sensing outside cct Voltage sense-- yes. I shall come back after a little study
Fine sir
regards
Sarma -
Hi
i have to check- may take some time -
Hi
Perhaps an LM323 can do your job but very costly compared to LM7805
In fact earlier MC78T05 (TO220) were available - I saw few of them -- these devices used to give 3 amps laod provided properly heatsunk.
if you get hold you may try -
Hi Audioguru
i agree with you completely-- power projects , for that purpose any project soud be built with proper discipline-- i was only teeling about lead loss compensation from the power supply to the load point--( say 50 to 100 cm for each lead). this itself drops the voltage and the resultant voltage at the actual load would be ( expected - lead drop). this could be compensated by a 4 wire system. that all.
regards
sarma -
Your temporary wires are too long and have too much resistance to properly measure the regulation of your circuit. A wire with only 0.002 ohms will create a voltage drop of 10mV at 5A...............
Hi audioguru
you may recollect the type of power supplies that had two more wires(4 wire method) and the lead drop was taken care of and the voltage is corrected at the load-- i don't mean that we can then use thin wires and take the reisk of fire due to I^2*R loss . in specific case where voltage drop is to be minimised, in addition to proper guage wirs, this remote votage monitoring and correction maybe adopte for this supply also.
regards
Sarma
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Hi Bobleny
Intead of asking whether someone is familiar with binary-- just think-- what heading you have designed-- i appeciate that you may perhaps be arning now--
coming to check-- i suugest that you try to breadboard it and have first hand experience-- or simulate on a softwaRE AND SEE WHAT HAPPENS- LIST YOUR PROBLEMS AND THEN SOME ONE CAN TRY HELP YOU REVISE THE DESIGN-- IT IS A PROCESS MY DEAR-- GOT THRO'.
However you have not defined the displays and their MAX value. Shall I imagine that LSD as seconds,with max of 9, next one is seconds(tens) with 5 as upper limit, and the MSD is units minutes with 9 as upper limit ??
sarma -
The simple most circuit for this would be to take the circuit chip out of a dead watch or a table clock. They use a crystal oscillator and dividing technique. You need to cut off the coil winding and add two diodes (IN4148) on both the outputs (P side of it) and join the N-side to get study 1-Hz clock.
Hi
it is working with a single cell-- you need to level shift to TTL or CMOS in order that it is useful
sarma
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Hi,
Lovely TOPIC. there are time signals broadcast terestrially. like 10MHz, 15MHZ and many other. they provide time ticks at 1sce-- these are controlled by atomic clock .
second , you should have DCXO- which provides a good standard clock and derive 1sec from this clock-- appears foolish is it not-- but when you used dead perfect 1sec pulse-- you may appreciate perhaps -
How can i create -
Hi Steven,
What a lovely homebrue construction.
Really fine. Congrats for theefforts and you have even damaged your finger while making this, I fear!!
Few doubt here, -
Hi
CD drive can play and the output caN BE HEARD BY ANY AUDIO AMPLIFIER-- BUT AUTO REPAT -- DOUBTFUL-- -
Hi Vivek,
this is a Pulse Width Modulation SMPS chip.
A good device in deed. I suggest that you may see the datasheet from www.alldatasheet.com
Variable Power Supply
in Electronic Projects Design/Ideas
Posted
Hi,
if you can scan the bundle of projects you find on the opening page of this site, you will go thro and you get a lot of data. eventually lot of diacussion posts are also on this topic and i am sure you will be stomach full .
all the best for 2k7