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Topic: Getting help to setup with voltage regulators and level shifters (Read 522 times) previous topic - next topic

twirap

Hi. I am a beginner to arduino and electronics. I see some cool things I can do but I don't know how to come up with the required resistor values or additional components I need in addition to the voltage regulators so I thought I could get help here on what electric components I need to build certain circuits. Below are the circuits I want since they are the most common logic levels.



I know most electronic devices operate on 1.8 V, 3.3 V, and 5 V logic. So what voltage regulators can I get to step down from higher voltage to the listed voltages of 1.8 V, 3.3 V and 5 V? Also, what valued capacitors and resistors do I need to build each of the voltage regulator? I don't know how you calculator the capacitor or resistor values needed for these circuits.


Secondly, the most common electronic devices that operate on 1.8 V, 3.3 V and 5 V logic will also need level shifters if I intend to use arduino to input to their buttons...So what level shifters can I buy for: 1.8 V, 3.3 V, 5 V logic operating level shifters and do I need any additional components like resistors or capacitors for these?


For each of the voltage regulators and level shifters, it would be helpful if you can tell me specific part numbers I can order.
The main purpose of this is that I like to modify lots of hardware and lack the knowledge of what additional components I need to use each of the main hardware and because I order most the hardware from chinese websites, it takes about 30 days to get to me and if I buy a voltage regulator and find out I needed capacitor for it then I have to wait another 30 days to get the additional components...This can really delay any project I want to work on.


Hopefully with everyone's help, I can create some batches of electric components so that I can assemble the batch to create the necessary voltage regulator circuit or level shifter circuit whenever I have a project without the long delay of asking around for the parts and waiting for delivery.

123Splat

Quick and dirty,

Google LM317 & LM337, download and READ the data sheets.  Linear Voltage regulators are not real efficient, but they ar very easy to use (if you follow the rules).

Level shifters: easiest way is to look up some on Sparkfun's web site and look at the schematics.  Or Google I2C Bidirectional Level Shifters.  Look up Philips Electronics I2C-Buss Specification (Page 43 in particular, try 1.2Kohm for R1-R4).

Chagrin

http://playground.arduino.cc/Main/I2CBi-directionalLevelShifter

The "use two mosfets" method works in most any situation. And also as stated on that page you can buy little modules with two or four ready-made circuits that implement this and then you'll be ready for anything that comes up.

When you're converting 5V to 3.3V or 3.3V to 1.8V you should use a low dropout (LDO) regulator, most commonly an LM1117. A 1117 has a 1.3V (max) dropout compared to an LM317 1.5V (minimum) dropout.

twirap

Thank you guys. I will order the parts you mentioned. Also, last question, I have a radio remote control and it operates on 9 V and I don't know what the pot values for the joysticks are. Is there a digital pot I can buy that is a fairly moderate value but not too high so I can replace the pot of the joystick without waiting for when the remote control gets to me? For example, should I buy a 100k digital pot since it can pretty much act like any pot from 1k-100k ? If so, how do I compute what resistor I need in addition to the digital pot? I see some random online schematics of a 10k digital pot used with a 500 ohm resistor but I don't get how they get the 500 ohm resistor value and if it even matters that you use a 10k ohm...if I just get a 1 million ohm resistor then I can just change its value through arduino to act like a 10k or even 1k pot. So why do the lower valued digital pots even exist and how do I compute the resistor value to use with it?

DVDdoug

Quote
should I buy a 100k digital pot since it can pretty much act like any pot from 1k-100k ?
In general, you can't make one value pot "act like" a different value pot.

Sometimes the value in't critical, and sometimes it is...    If you connect a pot between 5V and ground, with the slider going to the Arduino's analog input, almost any value pot will do the same thing...  In the mid position, you get 2.5V out.    If the pot value is low, you have more current though the pot, (and more power dissipation).   If the pot value is high, you can get noise pick-up and interaction with the high-impedance Arduino input and you might not get 2.5V.

In other situations, the circuit could get totally fouled-up if the pot value is off by a factor of 5 or 10. 

An important part of engineering (or modification/repair) is knowing when a component value is critical and when it's not.   That's not always an easy thing, because you have to understand the circuit it's used in.    Somebody might say, "Just use a resistor somewhere between 10 K and 100K", or "Use resistor around 10K."   Other times, somebody might say. "Use a 330 Ohm resistor", or if it's more critical, "Use a 330 Ohm 1% resistor."

If you are working with simple voltage dividers & resistor circuits, then an understanding of Ohm's Law and Kirchhoff's Laws may be all you need to know.    In other cases you may need to understand AC circuits, digital logic circuits, op-amps, transistors, MOSFETS, etc. 

twirap

I don't know whether I should be sad or depressed because I completed 2nd year of computer engineering which included hardware up-to mosfets and gates latches registers etc but when I do my own projects for my hobby and try to use electrical components, then I am completely lost on how everything works. Based on me  just computing the values of the components I have an idea of how it functions but I lack the information to build it. This is the entire reason I feel that by being at university I am learning theory but I am not learning jack **** about how to actually do it...Maybe engineers are suppose to design and not build so we wouldn't need to know theory but if that is the case then perhaps I am not into engineering because I love building.


http://i.imgur.com/v32ttc8.jpg
I understand this guy is using 2 op-amps but I don't know why, maybe to step-up the voltage for the buzzer? He has another op-amp for the button...Not sure why...He is basically using a 1.8 V level shifter to send pulses to 8 buttons of a nitendo DS and based on what sound the game plays his MCU will act accordingly.



Also, is there a book on electronics I can read that will teach me on how to build my own circuits rather than work hardcore on theory? I am already reading a book by Jeremy Blum on arduino and that includes electronics and circuit schematics but he never explains how he calculates the diode or capacitor values or why the capacitor is there so all I am left to is memorizing the schematic and asking around for what values to use if I want to use the same schematic as him.

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