| Electronics > Beginners |
| Beginner Components? |
| << < (7/19) > >> |
| JacobEdward:
--- Quote from: Simon on February 22, 2015, 10:10:48 pm ---JavaScript does not exactly sound like a microcontroller language. --- End quote --- Javascript is a turing complete language, what that means is there is nothing that any other language can do that Javascript cannot do (it just so happens that Javascript is directly built into the major browsers, can script a server, create offline apps, mobile apps, microcontrollers, etc.) --- Quote from: Simon on February 22, 2015, 10:10:48 pm --- I don't know what JavaScript entails as I barely understand C myself however I'm pretty sure you could do some stuff in C. --- End quote --- The hassle of learning a whole new language when I already know a language is not worth the effort (especially if there are potential compensations for an increase in Htz). Imagine deciding to learn Japanese or Hungarian because it might save you one or two (relatively insignificant compared to everything that needs to be done) extra steps in filing some business document... it would be different if you'd move to that part of the world, but if you're just going to be doing the same thing you would have been doing anyways... just go with the extra step --- Quote from: Simon on February 22, 2015, 10:10:48 pm ---The other thing I think you are missing is that any microcontroller will produce a square wave output where as usually you are controlling a motor with a sine wave. What is usually done is to approximate the sine wave with a varying duty square wave so that the average voltage of the PWM output represents the average sine wave voltages that you would otherwise supply the motor. This is why your variable frequency drives are not cheap, they are not necessarily simple. --- End quote --- Wouldn't it just be easier to programmatically control when some other voltage source will turn on and off that would be producing the proper signal for the motor? Either way, thanks for that tip, didn't realize there was this difference in wave forms... Also, is this true for DC motors or is it just for AC motors being controlled by a digital device? How is this approximation usually done? Is that just code within the micro or are there components that interpret the correct variations? --- Quote from: Simon on February 22, 2015, 10:10:48 pm ---The other thing is if you are using the PWM capability of your microcontroller once this is set up through whichever language you choose it should run very efficiently as it is a separate hardware peripheral on the microcontroller chip so I'm not sure how the programming language is affecting its top frequency. A bloated programming language may mean that it takes you longer to alter the PWM duty but the frequency should be achievable. --- End quote --- Changing the frequency isn't a problem, but it's definitely not capable of getting up to that 72Mhtz like it claims it can, which is why I keep asking about it being possible to control another chip that does nothing but create these incredibly high frequencies... is that possible? --- Quote from: Simon on February 22, 2015, 10:10:48 pm ---An operational amplifier or carry out any amount of operations as the name suggests on an analogue signal. You can use it to multiply or divide a signal or add signals together. Obviously the operational amplifier needs a power supply, the input impedance of an operational amplifier is theoretically infinite in reality it is still so high that you won't have to worry about it if you are controlling it from a microcontroller. Operational amplifiers are not usually designed to provide high current output they are mainly voltage amplifiers although there are many power amplifier chips which are essentially powerful operational amplifiers. But having said that they may not have the current capability you are looking for. --- End quote --- I'm not too familiar with impedence so I'll be reading that wikipedia tonight, but I know you said they're not suppose to provide current, but aren't you indirectly providing current when you provide Voltage... doesn't one come from the other through ohm's law? --- Quote from: Simon on February 22, 2015, 10:10:48 pm ---If you are looking to use a H bridge then you probably don't need an operational amplifier. You will need for MOSFETs to end channel and 2 P channel MOSFETs. --- End quote --- I have a bunch of bipolar transistors in the mail and according to their datasheet, they're able to Collector–Emitter Voltage VCEO 40 Vdc Collector–Base Voltage VCBO 60 Vdc Emitter–Base Voltage VEBO 6.0 Vdc which seems like it would be more than enough for any DC motor I'm going to get my hands on any time soon, right? |
| JacobEdward:
Something I'm not too clear on that hopefully you could explain is why voltage regulators are preferable to voltage dividers in conjunction with capacitors... what is a voltage regulator made of or is it just an IC of more basic components? I get the idea of using a voltage regulator in AC to DC conversions, but is there another necessary use case? |
| Zero999:
--- Quote from: JacobEdward on February 22, 2015, 09:16:19 pm ---I would have thought a Op Amp would be the solution to a mircocontroller not being able to supply enough Voltage or Current and use transistors to create the H-bridge... While looking into motors, it seems that I'll need more flexibility with frequency than what my microcontroller can give, is there an easy solution to this? The core chip on my microcontroller is about $5 and without any of the special code it can output 72 MHtz (it can barely give 5KHtz as it is right now) so I'm not entirely sure why I would need to spend hundreds of dollars on a variable frequency drive to control AC motors... --- End quote --- Because 72MHz is the clock frequency which will be much higher than the maximum PWM frequency the MCU can generate from one of its I/O pins. A variable speed motor drive does a lot. It converts the mains voltage to a stabilised DC bus, provides isolation between the AC side and control and has power factor correction. It will have many other components as well as the MCU: MOSFETs/IGBTs, opt-isolators, op-amps, huge electrolytic capacitors, inductors, radio interference filtering. A good variable frequency drive will also have to meet various standards for everything from electrical safety to efficiency. |
| JacobEdward:
--- Quote from: Hero999 on February 22, 2015, 11:01:20 pm ---A variable speed motor drive does a lot. It converts the mains voltage to a stabilised DC bus, provides isolation between the AC side and control and has power factor correction. It will have many other components as well as the MCU: MOSFETs/IGBTs, opt-isolators, op-amps, huge electrolytic capacitors, inductors, radio interference filtering. A good variable frequency drive will also have to meet various standards for everything from electrical safety to efficiency. --- End quote --- I would like to build my own variable frequency drive (it seems like a good device to learn fundamental electronics with), do you know any really good tutorials out there with an explicit BOM I can use? |
| rolycat:
--- Quote from: JacobEdward on February 22, 2015, 11:07:45 pm --- --- Quote from: Hero999 on February 22, 2015, 11:01:20 pm ---A variable speed motor drive does a lot. It converts the mains voltage to a stabilised DC bus, provides isolation between the AC side and control and has power factor correction. It will have many other components as well as the MCU: MOSFETs/IGBTs, opt-isolators, op-amps, huge electrolytic capacitors, inductors, radio interference filtering. A good variable frequency drive will also have to meet various standards for everything from electrical safety to efficiency. --- End quote --- I would like to build my own variable frequency drive (it seems like a good device to learn fundamental electronics with), do you know any really good tutorials out there with an explicit BOM I can use? --- End quote --- VFDs are primarily designed to drive powerful AC induction motors which operate at mains voltages and often require three-phase supplies. As such, they aren't a good choice for a beginner in electronics. If you are interested in controlling motors electronically, start with a low voltage DC motor and experiment with PWM speed control. Googling terms like "DC motor control tutorial" or "Arduino DC motor control" should give lots of suitable examples. |
| Navigation |
| Message Index |
| Next page |
| Previous page |