[sen2009]

I have found a simple circuit desginer -
MC34063A design tool

I need these parameters -

Vout = 14V

Iout = 500mA

Vin = 12V Vripple = 2500mv

Vin = 24V Vripple = 4000mv


Can someone please guide me in the components I need. The circuit seems simple enough to build on a normal dot matrix pcb.

[greenhorn]

prototype first. get a breadboard!

[sgiitk]

Originally Posted by sirius1845

why not try 7815 /7812 Voltage regulator chips. What is the current draw for the sensor?

A 7812 will require at least 14.5v to work. It is a 1A device but 5A devices are also available. I guess a transport vehicle with its 24V system should be able to provide the voltage. Similarly, a 7815 may not work much below 17.5V.

My own feeling is that he needs a constant voltage and the exact value is not that critical.

Also, adding another transistor to boost the output is fairly simple.

[sen2009]

Originally Posted by greenhorn

prototype first. get a breadboard!

Got the breadboard. Inquired in local electronics part market in Thane. They have inductors, capacitors and resistors. But they can't advise - I have to tell them exact part numbers.

Originally Posted by sgiitk

A 7812 will require at least 14.5v to work. It is a 1A device but 5A devices are also available. I guess a transport vehicle with its 24V system should be able to provide the voltage. Similarly, a 7815 may not work much below 17.5V.

My own feeling is that he needs a constant voltage and the exact value is not that critical.

You are absolutely correct sir. I need a steady voltage around 14V. It is not necessary to have exactly 14V.
Just now I installed one LM7815 in a 24V truck. The truck main voltage is playing between 22 to 29V. I have directly connected the LM7815. That is, Pin 1 to main line, Pin 2 to ground and Pin 3 to my sensor's input line.
I'll report the performance in a while.

My main issue is for the 12V vehicles. I have tried 7812, but its not giving me any stable voltage, not even a 10V.

[sgiitk]

Originally Posted by sen2009

My main issue is for the 12V vehicles. I have tried 7812, but its not giving me any stable voltage, not even a 10V.

It will not. So unless you can use a 7805 you may be out of luck.

Also, put smoothing capacitors on the input (100-500uF) on the input and output (0.1uF is enough).

[sen2009]

Originally Posted by sgiitk

It will not. So unless you can use a 7805 you may be out of luck.

Also, put smoothing capacitors on the input (100-500uF) on the input and output (0.1uF is enough).

OK sir.

How do I connect these capacitors to LM78xx?

Capacitor1 +ve to pin 1,
Capacitor 2 +ve to Pin 3

and Both Capacitor negatives to pin 2?

Will this work?

[shobhit]

Originally Posted by sen2009

Can someone please browse this site and tell me if there is anything I can use.
Online Shopping in Mumbai

No, there are none on this site. You should look at RS Components (as pointed by Low Bass Maker) or Element14. For 12V output you would find modules in quarter brick configurations, with input ranges typically from 9-14V, or a similar range about higher values (24-28). For a wider range you should use two different modules. I am assuming, on one platform you would have either of 12V or 24V available.
You would also have to look at sensor specification to ascertain the ripple allowed on supply voltage. If you are not too keen on online options, consider options from Switching Power Supply - Mean Well Switching Power Supply Manufacturer . NSD15-12S12 is the module that seems to meet your mentioned your requirements They are easily available in Bangalore, and should be available at your location as well.

[sgiitk]

@se3n2009; It looks like to be so. The caps are between the positive pin and ground (I do not remember the pin outs off-hand). The output I am told is more to stop the chip from oscillating. Even 0.01uF will do.

[shobhit]

Originally Posted by sgiitk

It will not. So unless you can use a 7805 you may be out of luck.

Also, put smoothing capacitors on the input (100-500uF) on the input and output (0.1uF is enough).

Another inherent issue with regulators is that for lower voltages they will not boost to adequate voltage level. And for higher voltages do consider the thermal dissipation. People burn boards quite often using regulators.

As a thumb rule, for most electronic designs supposed to work on power supplies being generated from a alternator/rectifier combination use DC DC supplies for sensors to function correctly. I don't think LM regulators are a solution here.

[pranavt]

In polarised caps, the negative goes to ground. Not sure what the pin2 in LM78xx vreg is.

Add decoupling caps on the input and output lines. In the range that was suggested above (100-1000uF, 40V min on the input side, 25V on the output line)

Use a breadboard to test your circuit. Buy a bunch of jumper wires to speed up the testing.

Automotive circuits need a bunch of shielding because it is a very unstable environment (voltage spikes, electromagnetic pulses, noise, etc).

[gostel]

Sensors are usually made less sensitive to supply voltage by using the bridge configuration. Not sure if your sensor has that. Linear regulators will prolly not serve the purpose, I guess. The Maxim MAX641 uses switching tech as far as I can tell. You have to hunt through the gullies of LammiRoad to hit upon a ready-made switcher regulator. Visha guys could direct you to the source if asked politely. Good luck with your search.

[sen2009]

Originally Posted by sgiitk

It will not. So unless you can use a 7805 you may be out of luck.

Also, put smoothing capacitors on the input (100-500uF) on the input and output (0.1uF is enough).

I have tried this. I have connected a LM7815 with 470 microfarad capacitor - input side and 1 microfarad capacitor on the output side. This is done on a 24V truck, and here are the results - ()for comparison, I am also posting data from a 12V truck with a LM7812 connected, no capacitors).


1. 12V truck with LM7812 - Regulated voltage



2. 12V truck with LM7812 - Fuel sensor output voltage


3. 24V truck with LM7815 and 470/1 micro farad filter caps - Regulated voltage



4. 4V truck with LM7815 and 470/1 micro farad filter caps - Sensor Output Voltage




With the filter capacitors, the voltage has stabilized a great deal. So, I guess I have a workable solution for 24V systems for about Rs. 35/-. Maybe, I'll get this circuit made at a better quality for around 50 - 55 Rupees. (as of now its in completely jugaad state - I have used a pair of nose pliers to twist legs of components together and the used normal insulation tape).

Originally Posted by shobhit

...

For 12V output you would find modules in quarter brick configurations, with input ranges typically from 9-14V, or a similar range about higher values (24-28). For a wider range you should use two different modules. I am assuming, on one platform you would have either of 12V or 24V available.
You would also have to look at sensor specification to ascertain the ripple allowed on supply voltage. If you are not too keen on online options, consider options from Switching Power Supply - Mean Well Switching Power Supply Manufacturer . NSD15-12S12 is the module that seems to meet your mentioned your requirements They are easily available in Bangalore, and should be available at your location as well.

Thanks for this great input.
I will check out in Lamington Road (in Mumbai). Do you have any idea of the price?
I have got the 24V thing working pretty much at the required level, so I need to work out only the 12V thing.

What is quarter brick configuration?

Originally Posted by shobhit

Another inherent issue with regulators is that for lower voltages they will not boost to adequate voltage level. And for higher voltages do consider the thermal dissipation. People burn boards quite often using regulators.

As a thumb rule, for most electronic designs supposed to work on power supplies being generated from a alternator/rectifier combination use DC DC supplies for sensors to function correctly. I don't think LM regulators are a solution here.

I think there are heat sinks available which can be mounted on circuit boards itself. Is that correct?

Originally Posted by gostel

Sensors are usually made less sensitive to supply voltage by using the bridge configuration. Not sure if your sensor has that. Linear regulators will prolly not serve the purpose, I guess. The Maxim MAX641 uses switching tech as far as I can tell. You have to hunt through the gullies of LammiRoad to hit upon a ready-made switcher regulator. Visha guys could direct you to the source if asked politely. Good luck with your search.

Thanks for the lead on the maxim IC. I will try to source something from Lammington road.
Also, I do not have knowledge of linear vs switching regulators. So, I guess a bit of reading up is in order.

I will post whatever I can find on this.

[low_bass_makker]

Increase the capacitor bank size to further reduce the ripple and more stable output !!!!

[sen2009]

Originally Posted by low_bass_makker

Increase the capacitor bank size to further reduce the ripple and more stable output !!!!

What could be a good value for the capacitors?

Will this work? -
http://in.element14.com/unbranded/b1...12v/dp/8689733

Or this one - http://www.murata-ps.com/data/power/ncl/kdc_nte.pdf

[ilangop]

Originally Posted by sen2009

I am trying to make an ultrasonic fuel sensor work in trucks with 12V or 24V systems. While the performance of the sensor is quite admirable, it suffers hugely from voltage fluctuations in the vehicle's main system.

I have tried a simple connection of LM7812. The vehicle I have installed this has a old battery which seldom supplies above 11.5 Volts. With the 7812, my supply to the sensor fluctuates between 10-11Volts. And, my sensor does not work.

Hi Sen,
If your requirement was a steady output voltage 14V inspite of fluctuations in the input side, I would suggest a car laptop charger. Those are SMPS type units with a switch to select the desired output voltage. You can grab one in ebay for about Rs 400/- or even at a lesser price from any of the electronics store. Upon dissecting the housing you will understand that the o/p voltage is controlled by frequency of switching. And the selector switch is actually toggling the R values to the RC.
You may even remove the switch and fine tune the system to the desired voltage witha single resistor. You can even bench mark the circuit and make multiple copies as per your need. That might work cheaper too.
I had purchased one for 12V i/p and it is capable of o/p till 19V, for Rs 300/- last year.
Cheers,
Ilango