New to the forums and looking for some advice

[Rhett]

I am looking to educate myself on electronics. I know the very basics (the function and symbols for most components) and can build things given a set of schematics, but I feel a bit lost designing my own.

I'm more a a visual learner so I like things that teach with pictures and diagrams rather than lengthy paragraphs. I also like stuff that gets straight to the point without a lot of needless filler.

If you guys could recommend some books or websites you think would be helpful to someone like myself I would greatly appreciate it.

The reason for this sudden desire to learn electronics is that I'm in the process of designing some circuitry for a project (it's kinda secret for the moment) I'm working on which should be pretty simple, but I'm a little confused about some parts of it. I also don't know the exact size of the motor I'm going to need yet so I'm kinda in the dark about how much amperage the circuit will need to be able to handle (shouldn't be too much though).

Eventually, I also plan to "digitally" control this project with micro controllers, but I'm saving that big hurdle of learning until after I get it working with more "analog" trigger.

If there's anyone that would like to have a look at the circuitry I'm thinking up and give me some pointers I'll try to draw it up on Photoshop (unless someone can recommend a better (free) program for making schematics).

Looking forward to picking your minds!

Rhett

 

[duke37]

There is a thread on this forum suggesting good books. You can also get a lot of information from Wikipedia.

 

[(*steve*)]

I'm more a a visual learner so I like things that teach with pictures and diagrams rather than lengthy paragraphs. I also like stuff that gets straight to the point without a lot of needless filler.

Visual is good.

WHat you need to think about than is electronics design as assembly of modules. Once you see a circuit that does something, it may have a module you can use later.

If you guys could recommend some books or websites you think would be helpful to someone like myself I would greatly appreciate it.

As for books, I recommend "The art of electronics", however it does require some existing knowledge. It has lots of examples, but it is a textbook. If you can find a copy in a library or similar, skip chapter 1 entirely and start browsing from chapter 2.

(it's kinda secret for the moment)

Try to get over the secrecy aspect. It's unlikely that your first design is going to be an earth shattering patentable design.

As long as you're not intending to break any laws of physics, we can help you.

OK, maybe it's a gift for your wife and she might read your posts (yes, we've had a project like that). In that case, I can understand

I'm working on which should be pretty simple, but I'm a little confused about some parts of it. I also don't know the exact size of the motor I'm going to need yet so I'm kinda in the dark about how much amperage the circuit will need to be able to handle (shouldn't be too much though).

If you're talking about motors, I expect you're wanting to do one or more of the following:

1) speed control
2) direction control
3) position control

Eventually, I also plan to "digitally" control this project with micro controllers, but I'm saving that big hurdle of learning until after I get it working with more "analog" trigger.

Discuss your requirements with us. The last thing we want to do (or you to do) is go down the track of a complex analog design that could be replicated digitally with much less effort.

If there's anyone that would like to have a look at the circuitry I'm thinking up and give me some pointers I'll try to draw it up on Photoshop (unless someone can recommend a better (free) program for making schematics).

Digikey have an on-line tool for drawing schematics. It's probably better than photoshop. In fact, paintbrush is probably better than photoshop for this.

 

[Rhett]

I'm a complete novice at this kind of stuff so forgive me if this schematic is hard to read.

As far as the whole "secret" thing goes, I know that the electronic circuit I need to make the device function isn't going to be anything special. It's the function of the device itself that is I believe. It's something I've tried to buy on multiple occasions over the last 5 years or so, but nobody makes it, so I've decided to make it myself and if it works as good as I think it will, possibly try to market it. The idea for something similar has been had by others (there are plenty of related patents), but none of them do it like I plan and nobody is actually producing a device.

If it was something that would better the quality of life for mankind, I wouldn't even think for a second about patenting it and would share the idea right away, but it's a total "luxury" item. It might be my ticket to getting some income while continuing my dream of traveling the world (if your interested in reading about my travels you can check out my blog at TheBeardAdventure.com)

There is 3 parts that I need to link together through a circuit

1. a powered dc motor
2. a small mechanical driven dc motor (being used in this case as an "analog" trigger)
3. and a bi-stable DPDT relay switch that flips when trigger changes direction and in the process turns itself off

Basically the POWERed motor spins in whatever direction the TRIGGER motor is being mechanically spun. When ever the TRIGGER changes direction, a electro-magnet is powered which flips a switch that turns it off (the purpose of which is a mechanical flip-flop switch that uses as little energy as possible).

I'm don't want any power from the battery or what every power source drives the POWERed motor to go into the TRIGGER motor, but I'm having trouble thinking of how to do that.

I would also like to only have one H bridge (I think that's the term for this type of configuration right?) but can't figure out how to do it without the PWM interfering with the power supply to the electro-magnet.

I'm also at a complete loss as to where resistors might be needed. The whole idea has always confused me. (For instance, if I put a small resistor in between the terminals of a car battery it will burn up, but if I add an led to the circuit everything is ok... why?)

If some of this sounds stupid, there's no need to tell me. I'm fully aware how little I actually know about electronics

 

[Rhett]

That schematic had a wrong connection. This is I think is what I was actually thinking (I'm very tired at the moment so it may be messed up too)

 

[(*steve*)]

OK, so what you want to do is spin a motor in one direction and have the circuit spin another motor in the same direction.

Do you want the latter motor to stop or continue spinning?

Is the speed of the second motor to be controlled at all (or should it just go at full speed)?

 

[Rhett]

The Powered motor should be spinning as long as the trigger motor/generator is being turned

speed isn't really the focus of the powered motor. It's purpose is to generate torque. I guess the powered motor could be shut off once it reaches it's top speed (because there would be no more torque at this point) but I wouldn't know where to begin with that. I had planned on just choosing a motor that accelerated the load slow enough that it wouldn't be an issue.

A PWM would also increase and decrease the amount of time it takes a motor to accelerate to its top speed given it had a decent load on it right?

I understand that motors consume more power at lower speeds (and also produce more torque), but I can't imagine a CVT that would be efficient enough for something this small to be worth the energy savings (if any considering it's torque I want and not speed)

So just to make sure it's clear, if the POWERed motor isn't creating any torque(accelerating), it isn't serving any purpose.

 

[(*steve*)]

I think you have a funny idea about torque. The morot does not have to be increasing in speed to be producing torque. If the motor speed is increasing then the torque being generated is simply in excess of what is required to turn the load at this speed. For an electric motor the torque produced is approximately equal to the current supplied to the motor.

From what you've said so far, I see no reason that PWM is required.

PWM is simply a method of controlling the amount of power delivered to the motor in an efficient manner. For a free-running motor (or indeed one with a constant load) PWM will generally allow you to change the speed. (And PWM is a method, not a thing)

CVT == Constant voltage transformer?

Before I go and design something for you, can you answer this:

1) does the first motor actually need to be a motor?
2) is the shaft of the first motor turned by hand, of by something else?

You're probably going to have to tell us more about your project, because I'm not convinced I understand exactly what you want. Whether that's because you're unsure yourself, or you just haven't explained yourself very well, I don't know.

 

[Rhett]

I understand that the motor can produce torque even if it can't produce enough to turn the load. What I need is for the motor to accelerate the load. From my calculations, 0.05 N-m of continuous torque should do the job. Granted that doesn't take in account for friction and other losses, but it gives me a ball park idea. I also understand that the amount of torque an electric motor provides is inversely related to the speed at which it is spinning.

The PWM which I plan to add to the circuit is just for fine tuning the device. From what I read, PWM works like an efficient dimmer switch which seems exactly like what I want for controlling how powerful the device is.

CVT = continuously variable transmission

1) No. all the trigger does is tell the device which direction it's going so the powered motor know which way to turn. I figured a small dc motor/generator seemed like an easy enough way to accomplish that.
2) It's turned by pulley type mechanism. I know different transistors require different amounts of voltage to the base before they turn on, and I'm not sure how a small dc motor will do at providing such voltage, but it shouldn't be too hard to change the ratios on the pulley mechanism to turn the generator faster if needed. I know it could probably be controlled by one of those tiny electronic gyroscope/accelerometer things and a micro controller (and I do plan on making a device like this in the future), but for the moment this is the way I think will work the best. Not to mention I think this first model it will be significantly cheaper than the micro controller one.

Thanks for being patient with me so far Steve. I really do appreciate the help

Rhett

 

[Fish4Fun]

Rhett,

I am going to take a SWAG at where you are headed: You want to use one electric motor to turn a second electric motor which will produce more electricity than you input into the first motor?

You really should be careful with this type of design, all sorts of people will tell you that it won't work, some of them may even appear to get angry! They will discuss seemingly ridiculous things like the third law of thermodynamics, like that as anything to do with perpetual motion!

Fish

 

[BobK]

Actually, a rotary encoder is what you want. It can tell the direction and speed at which a shaft is turning. This would be far more robust than using a small motor as a generator.

Bob

 

[Rhett]

Fish - Not even close. Although to be honest, a lot of what I know about electronics and physics I've learned by experimenting with "free energy" ideas over the last 7 years or so. This project has nothing to do with that, though it does incorporate some of the lessons I've learned. This project would be for a total "luxury" item that would be comparable to something like the dish sponge with soap in the handle.

Bob - I had to look up rotary encoders to see what they were all about. They do seem like a viable alternative and it is possible I could use one, but there are a couple issues I would need to sort out.
1. They have a digital output. I assume that means I would have to learn how to program micro controllers (which I will do for later iterations of the device if it works well). It would also still require the pulley mechanism which I don't want in the "all digital self contained" version I plan to design pending the success of the cheap prototype.
2. I'm not sure how well they hold up wear-n-tear wise. There will be a lot of spinning and changing directions
3. It would need something with very little friction with the ability to spin indefinitely in one direction. I suppose an encoder from an old track ball mouse or even the scroll wheel on modern mice might fit in that category.
4. It would need it to be cheap as possible and readily available.

 

[Rhett]

I went today and got an arduino uno. I was suprised at how quickly I was able to program it to do what I wanted after watching like 5 video tutorials on youtube.

Right now I've got a small dc motor hooked up to one side of a voltage splitter and the other side is connected to the 3.3v output on the board. This allows me to measure negative voltage from the motor (took me a while to figure out).

I have it hooked up to a small bread board right now with a variable resistor to control PWM and a red and green led to simulate the voltage that will trigger the H-bridge. When the motor spins one way the red led is lit, the green is lit in the reverse direction, and neither are lit when the motor isn't moving.

I think that takes care of the triggering, all I got to do now is figure out the power amplifying circuit. Will the schematic I posted on the first page work? Is there anything I need to add to it to protect the arduino board or anything else like the powered motor? and can someone explain the difference between transistors and mosfets to me in simple terms? I've googled it already, but I'm still confused.

My arduino code right now is pretty simple and looks like this. Pardon all the annotations (I'm a noob and it will help me in the future to remember what I did)

------------------------------------------
int ledG = 9;
int ledR = 10;

void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
// this sets pins 9 and 10 to be outputs
pinMode(ledG, OUTPUT);
pinMode(ledR, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
// there is a voltage splitter with the 3.3v power pin on one side
// and one side of a small dc motor connected to the other.
// the output goes to A0 and the other side of the dc motor goes
// to ground
int wheelValue = analogRead(A0);
// analogRead function returns values that range from 0-1023
// the analogWrite function is a PWM with value from 0-255
// this translates the prior values into ones that work with the later
int potValue = analogRead(A5)/4;

// this is just for monitoring whats going on
Serial.print("Pot =");
Serial.print(potValue);
Serial.print(" and Wheel=");
Serial.println(wheelValue - 337);

// using a voltage splitter, the value of wheelValue when the motor is
// still is 336-337. to give a little wiggle room i went +-10
if (wheelValue > 347){
// (pin#, 0-255)
analogWrite(ledG, potValue);
}
else{
analogWrite(ledG, 0);
}
if (wheelValue < 327){
analogWrite(ledR, potValue);
}
else{
analogWrite(ledR, 0);
}
delay(100);
}
-------------------------------------------------------------

 

[(*steve*)]

I went today and got an arduino uno. I was suprised at how quickly I was able to program it to do what I wanted after watching like 5 video tutorials on youtube.

I'm impressed.

Right now I've got a small dc motor hooked up to one side of a voltage splitter and the other side is connected to the 3.3v output on the board. This allows me to measure negative voltage from the motor (took me a while to figure out).

Now doubly impressed.

I was thinking along those lines but wondered how achievable it might be.

There are some issues with this, if you can show us the circuit you're using we may be able to recommend some enhancements. One example (if you don't already have them) is an RC circuit to smooth the waveform so the arduino sees the average voltage, the other is some diodes to prevent the voltage exceeding the supply rails.

I have it hooked up to a small bread board right now with a variable resistor to control PWM and a red and green led to simulate the voltage that will trigger the H-bridge. When the motor spins one way the red led is lit, the green is lit in the reverse direction, and neither are lit when the motor isn't moving.

Excellent.

I think that takes care of the triggering, all I got to do now is figure out the power amplifying circuit. Will the schematic I posted on the first page work? Is there anything I need to add to it to protect the arduino board or anything else like the powered motor? and can someone explain the difference between transistors and mosfets to me in simple terms? I've googled it already, but I'm still confused.

Mosfets require very little current to hold them on or off (essentially zero). Transistors require some proportion of the current they carry to keep them turned on (between 0.5% and 10%, depending on the gain of the transistor). The threshold voltages also differ as do the characteristics of how they switch.

I'll take a look at what you have posted on page 1.

Take a look at this page for H-bridges. It has some fairly standard configurations. Note that if you're using a microcontoller, you can dispense with any separate PWM and do it using the H bridge.

My arduino code right now is pretty simple and looks like this. Pardon all the annotations (I'm a noob and it will help me in the future to remember what I did)

The internal documentation is good. Most noobs omit it. Keep doing it.

 

[Rhett]

Here's the schematic for what I currently got as the trigger

 

[donkey]

hi Rhett nice work so far.
anyway I like what you are doing. I found arduino to be a very simple design with a huge support base.
anyway if you want to measure the rotation speed of a motor try using one out of a scanner. on one end it usually has a wheel and a sensor so that the motor turns very specifically. see if you can figure out how to program the sensor and post your code cos I know 2 people on this forum that would love to see it. (I am one lol)

 

[(*steve*)]

Here's the schematic for what I currently got as the trigger

That's not the way I would have done it, but it should work.

However, you can improve it so that you don't risk damaging your arduino if you turn the motor too fast. Also you can smooth out the pulses you get from the motor which may make the readings more consistent.

D1 and D2 can be any diode. I'd probably prefer a 1N914 or 1N4148, but you could use 1N4001 if you wanted. They prevent the voltage at the input of the arduino rising above 4V or below -0.7V

The capacitor (and you might choose something between 0.1uF and 1uF) will smooth out the pulsed DC coming from the motor so you see a more consistent voltage that moves more smoothly.

 

[BobK]

The AVR microcontrollers already have protection diodes on the inputs and state the input voltage limits as Vdd-0.5 to Vcc+0.5 V. So any external diodes must conduct at less than 0.5V in order to do any good. I would use Schottky diodes for protection.

Bob

 

[(*steve*)]

Yeah, I really should have suggested a series diode before the input pin. 100 ohms should be fine.

If that input capacitor has a voltage on it and the power supply to the arduino is shorted, the cap will discharge through the arduino's input diodes.

In this case, if the capacitor is small, and considering the impedance of the input signal, the arduino's input protection diodes are probably not at much risk.

 

[Rhett]

I've been tinkering away at building the mechanical parts of the device in my freetime for a couple months now. I've just about got it to the state where I need and and I'm attaching the electronics to it.

I'm also replaced the physical trigger/motor circuit with a 6-axis accelerometer/gyroscope thing. Took quite some time to figure out how to use the data coming out of it, but it seems to do the job pretty well.

Things are working pretty decent but the arduino is acting a little buggy when I have it triggering the drive motor. It never showed this problem when it was just lighting led's so I think it probably has something to do with interference from the motor.

whatever it is, it cause the arduino to freeze up every now and then in any of it's 3 possible states (forward, reverse, pause) and stays that way till it gets reset. At first I thought it might have something to do with the gyro, but the serial communication doesn't seem to show anything odd in the frames before it freezes up.

the motor that's driving the device it this one from radioshack
http://www.radioshack.com/product/index.jsp?productId=2102827

I'm driving the motor off a 12v battery. The arduino is running of it's own 9v battery. The GND on the arduino board is connected to the 12v batteries ground.

any of your thoughts on the potential issue would be appreciated.

here's the schematic of my current setup.