How to decrease the voltage?

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sunny

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Joined 2004
#1
Hi Friends,
I have Yamaha PSR-3000 electronic keyboard and it needs 16 volts switching power supply and i dont have company adapter and at present i have another switching power supply adapter of 19 volts DC of 3.42 Amperes and my keyboard requires 16 volts DC,2.4 Amperes.
So what resistor i should i use in series to get 16 volts,2.4A from 19 volts,3.42 power supply?Your help is highly appreciated and please give the resistor value and its wattage.

Thanks,
SUNNY.
 
#2
Inserting a resistor in series with the supply isn't a good way to do the job. If you were going to power a light bulb you could use that technique, but you risk destroying the keyboard because it doesn't draw a constant 2.4 A from it's 16V supply.

Switchers (and all other voltage regulators) constantly compare the output voltage to a stable reference. If you tweak the reference voltage you can set the output to 16V. That can be done with a resistor or two, but you have to find the reference in the circuit.

I_F
 
#3
I_Forgot said:

Switchers (and all other voltage regulators) constantly compare the output voltage to a stable reference. If you tweak the reference voltage you can set the output to 16V.

That can be done with a resistor or two, but you have to find the reference in the circuit.
.
Click to expand...



Yes.
If you could draw exact circuit with resistor values
at that reference point or PIN of that switch supply
it wouldn't be hard to give directions.
If you posted it.

There are many in forum that are Really Power supplies EXPERTS.
Even when it comes to complicated switching circuits.

But this might not be so easy to do.
Probably not a schematic of that supply to find in internet
and to draw a copy just from looking at PCB, is often difficult.


Hope you can solve to get a good 16 Volt supply.
Otherwise, how can you be happy this Christmas🙂

lineup
 
#5
Not a PRO solution...

This is a quick solution
see attachment

TIP 122 should be mounted on a heatsink.
5K6 resistor should be 1 Watt
Connect 1k resistor at the output and measure the output voltage. Confirm it is correct and then connect as needed to the keyboard.

Gajanan phadte
 

Attachments

  • 19 16v.jpg
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#6
Hello Gajanan phadte,
Thanks for your circuit,now i'll purchase the components and i will try this circuit for my keyboard and is this 560,100ohms resistors of 1/4 watt?and is 0.1 disc ceramic?
Instead of using this circuit and if i simply connect 3 or 4 BY255 in series,is there any problem?please clarify.

MAY GOD BLESS YOU.

Thanks,
SUNNY.
 
#7
sunny said:

Instead of using this circuit and if i simply connect 3 or 4 BY255 in series,is there any problem?please clarify.
Click to expand...

no, i dont think so.

If you buy a number of Diodes whatever type that can take at least 5 Ampere
than you should be able to see how many diodes you need
to get ~16 Volt.

I have used this way in some cases myself, to get smaller Volt Drop.

I think it will be just fine,
because a circuit like you will use, is not require precise 16.000V.

Think about in car .. stuff you use in Car,
will work well and can take any voltage: within range like 11.5 Volt - 16 Volt.
If what you put in your car, can not take this
then it is not suitable for car battery/car generator use.
==============================================
==============================================


Go for simple but good:, your own solution:
Buy a number of 5-10 Ampere diodes.
Not critical what type, as long as they can take 5A.

Than make some tests:

1) Start by adding 5-6 diodes!
2) If voltage is below 16 Volt, than remove 1 diode
and repeat until you get 16.0 volt, or just a litle bit MORE.
Maybe 16.1 16.2 16.3 Volt.
3) Then I am almost sure this will work forever!


Think will be no problem at all for get gear working
before Christmas 2006.

Have a good time!
lineup
 
#10
Hello Friends,
I have played my keyboard for the christmas programmes very well using the modified switching power supply.I have connected four 6A4 diodes in series on positive line and i'm getting 16.5 volts at the keyboard.
Now another problem has started,the four 6A4 doides are getting too hot and they are burning my fingers if i touch them,I can't understand why the dodes are getting very hot ?The current rating of diodes are 10A and my keyboard requires only 2.5 A.
Is there any solution to this problem?

Thanks,
SUNNY.
 
#11
does not need to be any danger
our fingers can not take the heat that semiconductors can

what this indicates, is that keyboard draws High Current
and so the power in diodes is quite a bit.

19-16.5 ~ 2.5 Volt
say 3 Ampere
Power dissipated in diodes= 2.5V x 3A = 7.5 Watt.
-----------

What you can do:

1. place these 4 diodes not to close to eachother
2. place them in free air = not close to any PCB surface
this will allow air to flow and COOL from ALL sides of each diode
3. usually we can let the pin of such HOT devices be a bit longer
so that the body of device is LIFTED like 5 mm ABOVE PCB

Other components like small resistors etc. have there body close to board
to reduce the length of connection pin.
This is generally good.

But for HOT diodes or POWER Resistors (without Aluminum heatsinks)
can be good to keep them a bit up in air.

*************************************************

If you still worry about heat in your diodes,
there are Rectifier Diodes in TO220 package.
Which allows you to screw a little Aluminum metal piece onto diode.

TO220_DIODE.png

This image shows a TO220 package, with one diode.
Has got 2 pins, instead like a TO220 transistor = 3 pins

****** sidenote:
TR-ansistor
TR-iode
---> the TR comes from TRIO = 3

TRiode - 3 pin diode (a sort of Tube / Valve, which was before all Transistors)


Lineup
Lineup Audio knowledge Bureau
http://lineup.awardspace.com/
 
#13
power diodes higher current TO220

sunny said:
What is the number of this 2-pin TO220 rectifier diode?

SUNNY.
Click to expand...

There are many.
Check the website of your Electronics Dealer.
Browse:
Components - Semiconductors - Diodes ....
And look for single diode in TO220 package(capsule)
that is rated something like 5-10 Ampere.

Maybe someone member from your neighbourhood, country
would be so kind give us
a Link to supplier or Part Number of one such suitable Rectifier Diode.

All the big semiconductor manufacturers make such high Current Diodes:
SGS Thomson, Philips and them from Japan, Korea, China, too.
There are plenty of variants for different voltages and currents.

lineup
 
#15
sunny said:
still i cannot find this 10A rectifier diode.Please suggest me suitable low cost 10Amperes diode.

Thanks,
SUNNY.
Click to expand...

So what is the website to Big electronics components supplier
in INDIA.

I can go there have a look for you.

Members from India, where are you, this christmas?
🙂


lineup - knows there are several other active and good members from India
 
#16
IRF has got a line of such diodes in TO220 package

The thing is maybe to find a supplier, preferably in India
or not too far from you.
But if you can buy from other countries, like from Online electronic web shops, then is no problem.
Like Singapore, Hong Kong, Japan etc.
If you live near New Dehli you can go buy them in a shop, for sure.

Here are 2 suitable diodes from International Rectifiers www.irf.com
Two TO220 power diodes from - irf.com - International Rectifier

They are called:
10ETS08 ( 10A, 800 Volt ), 10ETS12 (10A, 1200 Volt)
You would only need max 100 Volt, so both of them will do, more than enough!
10ETS08 Datasheet PDF - with details


These diodes will cost you more money, than if you go for normal Axial 2 pin Power diodes.

I think those you have now ( 6A ) will do well
- if you put them in free air for some cooling ( see my prev. post )
but of course you can upgrade to 10A, if you like.


lineup
 
#18
sunny said:
Can i use 10A1 diode?i think It is a Axial 2 pin Power diode and is this diode costs less than 10ETS08 or 10ETS12?

SUNNY.
Click to expand...

Yes 🙂
this would be perfect - and better price, if you can find a shop.
🙂
Generally it is good to have some margin:
Use 3A diodes for 1 ampere currents
Use 6A diodes for 2 ampere
Use 10A diodes for 3-4 ampere

The same goes for Transistors and Resistors.
No components will work at best,
when they have to do HEAVY WORK.
Same goes for people.
A little child can not carry so much weight, in a good way,
as a big mother can.


See my attached Picture, with Image and Details
of 10A1
The manufacturer is called Rectron
datasheet:
http://www.rectron.com/data_sheets/10a05-10a10.pdf

10A1
It is an axial 2-pin power silicon rectifier diode
FEATURES
* Low cost
* Low leakage
* Low forward voltage drop
* High current capability
* High surge current capability
MECHANICAL DATA
* Case: Molded plastic
* Epoxy: Device has UL flammability classification 94V-O
* Lead: MIL-STD-202E method 208C guaranteed
* Mounting position: Any
* Weight: 2.08 grams


lineup
 

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  • rectron-10a1.png
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#20
sunny said:
Thanks a lot for helping me.Now my problem has completely solved.

SUNNY.
Click to expand...

As you can see in Datasheet FIG.2,
FIG. 2 - TYPICAL INSTANTANEOUS FORWARD
CHARACTERISTICS
the 10A1 power diode
has got a voltage drop ( VF = forward voltage )
of something like 0.8V at 3A

so we can think
3 diodes would have a drop of ~2.4V
4 diodes would have a drop of ~3.2V
.... something like that


you are welcome back
if there is anything else you want to discuss or ask
in electronics

as you know, we are many here
that could possibly try to give advice


Regards to sunny, India
from lineup, Europe
🙂
 
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