CasualKilla

Thankyou, very good insight, I noticed the voltage actually does reduce slightly when the resistance of the base circuit increase, I was looking at the current, which increases slightly with decreasing resistance. You are 100% right, reducing the resistance drastically reduces the pulse width and pulse voltage.

it is about 200ns, I think you are right, it must be current discharging across the CE junction It seems when Q1 and Q4 are switch on with the input switch switch, there is a pulse of current that flows out the base of Q2 and Q3, weird. I can increase the value of R3 to reduce this current spike though... The pulse seems to be caused by a 4.5V spike at the base, does not seems to be effected by the addition of the diodes or changing the resistors.

I am a bit unsure about the diode selection, what are the different applications for silcon vs schotty diodes, and what kind of current rating must the diodes be speced for? 2.5A since that is the max motor current? And no, that is from a LTSpice simulation, I have not built the circuit yet.

I see, I can handle the math though . It is just not always clear what the wattage spec is. We just have shelves of the cheapies here in the lab. New POST I may not have access to BJT, but I can get N-channel MOSFET's (60W). Could I use a circuit like this? Also, if mosfets will work, how do I drive mosfets "hard-on". For BJTs I just designed the base current to be large enough to break the minimum Ic = hfe * Ib ratio given in the datasheet, which makes it saturated with very low C-E drop. I assume there is also a maximum Vgs I must avoid for mosfets?

Thank you for that post, I believe I was using a 1/4 W resistor . In terms of the diode, do I need to find a Schottky that can handle more than 3A? Also can anybody explain the current spike in R1 (also happen in R2, but much smaller). Is it perhaps due to my lack of diodes?

I designed my circuit for a particular base current to force saturation (hfe = 30 from datasheet). But you are right, smaller Resistance should lead to less heating I^2 * R. Anybody know what kind of max current these std resistors can handle?

Yes, I have just test my 100 ohm resistor at 12V and indeed it does burnout after some time, this is a real issue... (using a 200 ohm resistor at 12V heats up alot, but its still going as we speak) I plan to use constant DC pulses, something like this: (the other winding will have its own circuit, this is just for one of the windings)

Hmm yes, the inductance of the coils, good point. I have come up with this solution, its a NPN H-Bridge modified to work with 2 inputs, but this seems to do the same job as ous previous idea. I guess I should check tomorrow if our DC supplies can do the V+ V- thing first. This is the final design, seems to work well, besides the diodes, are there any other components I should add, like capacitors?

I understand the H-bridge well, but it uses 4 inputs, I would like modify/add on to the H-bridge to use a single switch just to flip the motor polarity. So i can use one switch for each winding, then one switch to connect/disconnect the Vdd. Thus 3 total. That would be ideal. I thought of this idea, but I would need 2 voltage sources and I run the risk of shorting Vdd to -Vdd which sounds very unsafe.

Ah ok, so I NEED to be able to switch polarities. Unfortunate.. So I pretty much need a circuit that switches the polarity of the phase with a single output switch, that would solve all my problems.... Is it possible to modified the H bridge to work with one input, input = 1 A positive, B negative then input = 0 makes it the opposite?

Yes, I have been trying to create that output sequence, but my PLC makes that difficult, how would I set each pin to Ground or Vdd using my outputs (I would need to use 8 outputs)? Could you purpose a circuit that uses less outputs? (also that looks looks a 5 wire stepper, I have a 4 wire) How do I need to energize these coils to rotate the stepper in one direction?

The winding resistance is 5ohm, I measured it today. Other than than I have no useful info on the motor. The plc is connected to "digital" outputs on the tutor board that short the two output ports when on, and open circuit the two output ports when off. I only really need one rotation direction, I need to rotate an object in steps of 45 degrees Will this circuit work for one direction rotation? (any tips on the voltage I should use would be appreciated)

I need to program a 4 wire stepper motor, problem is, there is no data sheet and no control circuit and i am completely lost. Can somebody please assist me with the ladder logic program to get it up and running? I have access to a decent PLC, and my only option is to hard code this, a control circuit is not an option.

Hi guys, I am looking to calculate the moment of inertia (J) and viscous friction (B) for a prototype motor connected to a fan load. The motor is powered with a constant voltage 3 phase supply and a torque sensor is connected in-between the motor and fan (figure 1). The torque sensor can give transient data of both torque and speed. figure 1: I have not tested the fan, but research seems to indicate the fan torque-speed curve will follow a quadratic curve like the one shown below. figure 2: I am assuming the bearing friction should have a fairly constant value B, however, the air resistance will cause an effective B that is dependent on the speed. By assuming the torque-speed to follow a perfect quadratic trend, I can convert the differential equation into a non-linear form with 3 unknown constants (eq1 -> eq4). figure 3: I have an idea to simply take 3 time points and on the start-up or shut-off transient response, and then solve equation 4. But I have concerns about the validity of equation 4 and the possibility of torque ripple from the motor. I have 2 questions: 1) Is my model correct, or correct enough (this is engineering after-all). 2) How would I calculate these values experimentally with the given setup in figure 1.

Hi there gents I managed to find this function which converts a 2 byte hex to 2 byte BCD, but since 2 bytes of hex can hold a decimal value 0 to 255, it is limited to a hex value between 0x00 and 0x63 (0 to 99). uint8_t hex2bcd (uint8_t x) { uint8_t y; y = (x / 10) << 4; y = y | (x % 10); return (y); } I need some help adapting this to produce a 12 bit (can use a 16bit variable) BCD output. I have developed my own code, but it is very very long and highly inefficient, so I am looking to use the simplest code and/or fasted code possible. CK edit: came up with this, which doesn't seem to work. uint16_t hex2bcd12bit (uint8_t x) { uint16_t B1; uint16_t B2; uint16_t B3; B1 = x & 0x0F; B2 = (x & 0xF0) >> 4; B1 = B1 % 10; B2 = B2 + B1 / 10; B3 = B2/10; B2 = B2 % 10; B3 = B3<<8 + B2<<4 + B1; return (B3); }

That is completely untrue. Everything i said is contrary to that. Perhaps try reading my posts in full if you want to comment on my intentions.

Brad nobody said you cannot post your opinions, but either admit to it being an opinion, or just be damn sure you back it up with some credible evidence, or you will receive alot of negative feedback. People don't like opinions trying to hide as facts. Firstly, the statement: "reincarnation has been proven by science, google it!" is gonna get some serious flack if you don't show this proof. Sorry yo tell you, but 1 book written by one person does not constitute proof in any world. I could find you thousands of books on aliens and ufo's, all claiming to provide evidence. The thing is, the evidence needs to be examined and experiments repeated until there is a scientific consensus. People's bias creeps in way too much, and you should try use your critical thinking to separate a fringe pseudo-scientist from the majority of scientists. Most scientists create theories to fit evidence, and then put those theories through rigorous peer reviews to test their validity. If this is your belief, then fine, but do not pretend that it is backed by science, where any respectable scientist would call Dr. Stevenson a quack or pseudoscience at best. Do you remember when there was a Docter who claimed vaccines cause autism. He was later exposed as rigging the studies and even admitted to lying, but still people believe that vaccines cause autism. Unfortunately, even today there are people who argue against vaccines and quoting "studies" that idiots like this created, many of them even know he has been discredited, but they brush it off as a drug company conspiracy plan. Do not be that guy who only sees what he wants to see, try and look at both sides, and pay attention to the credibility and the amount information coming for each side, then come back here when you have thoroughly researched the issue.

With combustion fuels, the efficiency is normally driven by temperature difference between the inside and outside of the engine. Cars in northern canada are much more efficient than cars in Equitorial New-Ginea for example.

I am appalled at the lack of imagination in this forum, just because they cannot progress the same way humans did, does not mean they cannot progress. With 2 to 3 times human intelligence and no religious shackles, they should atleast make some form of progress every say 100 to 1000 years, surly they will be able to space faring technology eventually. There is no time limit here wtf,

The space shrimp move in seemingly random pattern, but the patterns actually represent complex vector functions, this is what drove the space dolphins to develop such amazing intellect (2 to 3 times human IQ levels) to predict space shrimp movement patterns.

Lets setup a solid backstory for these creatures. They are about 3m long and resemble dolphins (call them space dolphins), but they do not breath air. They also have very good communication adaption, but mainly use sight to hunt. They do not have much is the way of disposable thumbs, and are only really able to manipulate objects with their mouths. But, these creatures are highly, highly intelligent, perhaps 2 to 3 times the IQ of a human. This was the result of million of years of evolution hunting a life-form resembling shrimp, but able to move with extreme speeds and change direction rapidly. These shrimp travel in packs and when disturbed start move as a group. The movement of the group often resembles beautiful patterns. The space dolphins study the patterns and using there massive intellects are able to predict the movement of the shrimp to a certain degree of accuracy. naturally, the space dolphins who could better predict these movements fared much better, and the shrimp who could move with increasing complex patterns survived longer. Hence the cycle continued until the space dolphins intellect raised to a level where they essential perceive the world as numbers, vectors and calculations. Not only can they peer into the future like humans, they intellectually place probabilities on future events and act accordingly. Like humans, they are fiercely protective and loving of their young and their own communities, this is because space dolphins working together are much better at hunting. Their huge intellect makes them very inquisitive of the universe, but due to their tendency to place probabilities on all events, they never develop any religious ideas. They become aware they they have become much more effective at hunting their prey than their prey is at escaping, and thus restrict hunting in certain areas as needed by developing a government. They also actively work to enhance the environment of their prey so they can breed faster sparking scientific study. They reach a state where they no longer have to compete for survival, and there inherent intellectual makeup leads them to endlessly study the world to satisfy their unquenchable curiosity. Will these poor space dolphins will forever be trapped in there useless bodies and watery prisons. Will they overcome the seeming necessity for opposable appendages and make due with their mouths? Will there technology reach saturation due to the limiting environment of watery world? Or will their amazing intelligence and immunity from human vices of superstition lead them into the cosmos where they will save earth by destroying the cancer that is the human race #nohippie?

No, there is no dry land, that is the whole point

That pilot was a real piece of work, people like that should just kill themselv... wait. Nevermind. Strange that some people make arrangements to minimize the impact of their death on their loved-ones, but them some asshats want to take the world down with them. He was clearly mad at the world for something. Probably a racist that blames his inadequacies on immigrants and such. Then again, he seemed reasonably successful, it could have been a more deep rooted mental health problem.

Aliens are real. How do i know? They tuk ur jerbs!!!!

Good advice friend. We do get given design problems, so it is not as bad as just asking us to solve given circuits, but still feels lacking sometimes. Perhaps the most annoying thing though, is that the physics is often so simplified that it becomes confusing and misleading, especially if you are the type of person who likes to use new understanding to make predictions. This has never been more true than when I starting studying electro-magnetism. The simplified explanations I looked at gave me incorrect intuitions leading to bad predictions. It was only after I started working through the fundamental maxwell equations that things started coming together, and even then, I made false predictions until I examined the conditions under which the equations were derived. I also think field lines are a terrible substitute for a vector field, only after a the vector field is understood, are the field lines even useful. The process was restarted when I looked into special relativity, luckily this time I got straight into the implementation of the equations, which provided better intuition about relativistic effects than some someone like Micho could have given in a 3 hour talk. Simplification is very dangerous when trying to make predictions, it only seems useful as an attempt at peice of mind for the ignorant.