stable dc-dc converter

[fever]

hello all,
i need a dc-dc converter for powering my tachometer.my motorcycle uses 12v battery. in normal condition voltage is 12v.but while running voltage increasing to 13-15v max.iam afraid this might burn off my chip.so is there any converter which takes 11-15v and give constantly 12v output supply?

and exactly for 5v shall i use 7805?or is there any other device which will handle this situation in a better way.
thanks

 

[Styx]

have a look into TRACO dcdc converters, they are simply the best
you can get ones which have a 9-18V input range and output a regulated rail dependent on the part you want

 

[3v0]

Search the forums for threads where people have built power regulation systems to use electronics in cars. You should find it interesting.

 

[sundeep jangra]

remote control cicuit

I have require a remote control cicuit for toy car.

Please send me the circuit.

 

[fever]

thanks i'll do that.can u guide me with some search words...
@sanpeed
before posting any data just have a look what and where ur posting.i hope u got my point.

 

[3v0]

Searching here is a bit of an art.

Start with 7805, car OR auto

The 7805 is a 5V regulator.
In the search results you should find other words that can be used as keywords.

 

[Sceadwian]

If you want to get 12V regulated from 11-15 you'll have to use a switch mode supply, linear supplies can not raise the output voltage above the input voltage without switching.

 

[3v0]

He wants 5 volts.

 

[Sceadwian]

I probably should have read that last line.

 

[fever]

well actually i want both 5v and 12v supply.
i want regulation which produce less heat.

the area where iam going to fit my tacho is around 50mm in dia with very less width.so i shld need a design which uses less number of components.and the area is fully closed,so can't think of heat generating regulators.

any more ideas regarding this issue will be appreciable.
thanks

 

[gootee]

Instead of the 7805, an LM2937 should be better for automotive-type applications.

- Tom Gootee

**broken link removed**

-

 

[phalanx]

I have require a remote control cicuit for toy car.

Please send me the circuit.

Did you crash your Hayabusa a little too hard?

 

[3v0]

Do you need 12V to power the circuit ?

 

[fever]

yes 12v to power tacho and 5v for battery voltage indicator circuit.

@gootee
LM2937 seems to be good.but can it handle rough both the lower and higher voltages according to the output voltage. imean from 10.5 to 15v input the output shld be 12v stable.

 

[Hero999]

Why do you want 12V?

A SEPIC converter will do that.

There are ICs around that make building such a switched mode power supply easy.
https://www.google.com/search?client=opera&rls=en&q=SEPIC&sourceid=opera&ie=utf-8&oe=utf-8

Please also post the schematic, your circuit might run of 10.5V to 15V without modification.

 

[fever]

its a lm2917 based tacho with LM3914 as led driver.i know lm2917 is built for higher voltages but i want to feed it exactly 12v so that it will live long.u know automotive conditions are very rough and rapid.and another issue is i have only one LM2917.i got after searching a lot(in my area they stop importing this chip,and online purchase is not possible for me) so i don't want to spoil it.
and ultimately the whole circuit is designed to work with 12v supply.

 

[audioguru]

The LM2917 has a built-in 7.5V zener diode regulator. The datasheet shows how it is powered through a 470 ohm resistor then the LM2917 circuit operates from the regulated 7.5V from the zener diode.
Then you don't need a separate circuit for 12V.

The LM3914 operates from 3V to 25V and has a built-in voltage reference and all the LED outputs are current regulated so you don't need a 5V regulator, just a resistor feeding the LEDs will get hot instead of the IC or the 5V regulator getting hot.

 

[Hero999]

It sounds like the whole circuit will work from anywhere inbetween 10V to 25V so trying to run it from exactly 12V is a totaly waste of time. You don't need a DC-DC converter!

 

[gootee]

yes 12v to power tacho and 5v for battery voltage indicator circuit.

@gootee
LM2937 seems to be good.but can it handle rough both the lower and higher voltages according to the output voltage. imean from 10.5 to 15v input the output shld be 12v stable.

Well, of course not. But neither will a 7805. They are both Linear Regulators. And I thought that we were talking about the 5V output. But even with a 12V LDO (Low Drop-Out) linear regulator, the input voltage has to be higher than the output voltage, by at least the drop-out spec (and a little higher is usually better), for it to be able to maintain the output at 12V.

You'd need a switchmode power supply, to get 12V output for input ranging from 10.5V to 15V. I suggest that you either download LTspice (aka SwitcherCad), at linear.com, and use the "File" - "Switch Selector Guide" automatic SMPS designer menu-option, or, go to national.com and use their on-line automatic SMPS designer. Then maybe also look for appnotes about snubbers for SMPSs. You might also want an LC filter on the output. And you'll probably want a 12V LDO linear regulator after the output.

If you meant to say "5V" instead of "12V", then yes, the 7805 and LM2937 "should" both be able to do it, although they might dissipate a fair amount of heat, especially at the higher end of the input voltage range. And the 7805, at least, might not be very happy about it, and might tend to fail. The LM2937 is a little more robust.

At any rate, it sounds like you should listen to what audioguru and Hero999 have recently posted, about your ICs' voltage requirements, and avoid some wasted time and resources.

- Tom Gootee

**broken link removed**

-

 

[fever]

thanks for the info guys.i'll do that with the 2917 tacho design.
and why asked for both 5v and 12v bcz i had another design in my mind.which uses 5v input
**broken link removed**

and it seems instead of wasting my time on only psu unit i think i shd concentrate more on tacho working.
thanks once again for sharing knowledge with me.