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Everything posted by Theatronics

  1. I've blown them up. :o magic smoke escaped, parts flew, blown up. That protection stuff works for well designed circuits. when you just plain abuse them, they go poof. -Mike
  2. That’s a tall order. How far does this signal need to travel? What you are describing is a CW signal. A signal that is just a sine wave at a given frequency. Morse code was sent using this method. The problem with CW signals is that they are easy to fool and are prone to interference. Most systems modulate the Carrier frequency (Carrier Wave) with a second frequency or even a digital signal. This insures that the signal can be identified from all the background noise an open CW receiver may pick up. Building a reliable Transmitter / Receiver pair is not a project for someone unfamiliar with radio theory. Not only are there lots of issues with the design, there are laws about the usage of the radio spectrum, if you mess up someone’s TV or phones they could complain and you could get fined. My advice is to find a prebuilt pair and use them. There are many such systems available. Remote controlled cars and airplanes have good range and are easy to interface. Look for Garage door opener retrofit kits. Also there are home security systems that are used to detect mail boxes being opened. All these are good prebuilt systems. All you would need to add is the connection to the car and the signal at the other end. Unless you really want to learn RF theory ? The basic method : Put together two tanks (a Cap and an inductor) that are tuned the same. Using the tuned frequency, Calculate the length of the antennas needed. (The distance an electron can travel at the speed of light in the time it takes for 1 cycle of the circuit) Attach a wire that long to one end of each tank. Ground the other end. Then Inject a signal into one tank at the selected frequency. The second tank will begin to oscillate in tandem with the first one. (Magic but it only works over a few feet) For longer ranges, additional parts are needed. Here is a low wattage Transmitter for example. -Mike
  3. close, I think they just put the same part in a cheaper package. there is no differance between a 7805 in a TO-220 case or a TO-92 case. They are the exact same die. But the smaller TO-92 case will pop like a firecracker if you try to pull 2 amps through it. -Mike
  4. Why would you ever want to do that ? Basics? Well The ratio of turns determines the voltage. 10:1 will convert 10volts to 100v. The number of turns will determine the Power. The more turns the more power. (It has to do with a measure of the coupling between the coils. The whole thing is very complex.) If a transformer is rated at 12 @ at 25ma, if you draw more than 25ma the internal resistance of the wire in the transformer will start to drop the voltage output. In effect you could simply measure the transformer in VoltAmps (watts) and then a 12v @ 25ma transformer would be the same as a 6v @50ma unit. The down side is that while the magnetic part of the formula is solid, the thermal part is out of whack. Because now the windings are handling more current than before and they will heat up more. If the physical size and shape of the transformer can't handle the heat it will melt down. And then there are the mind killers. Flux leakage, Q Factors, Harmonics, Phase shift, and even Inductance mismatch (Depending on the frequency you will be working with if the two coils Pri & Sec are not matched to the frequency you would loose a lot of power even with everything else just perfect!) Let us know what your goal is and maybe we can guide you better. -Mike
  5. (I am assuming US style phone system here so forgive me if I am off target) The phone line expects to see about 600Ohms per unit. The main issue I have always dealt with is the ON/OFF hook changes in the system. Idle the system sits around 60v Ringing is around 90VAC @ 20hz Offhook and in use the DC component is around 40v Here is a link to a wealth of Phone interfaces. http://www.tkk.fi/Misc/Electronics/circuits/teleinterface.html#audioint -Mike
  6. Remember your basics. P = E * I. If the Voltage into the chip is 9V and the voltage out is 5 then there is a 4V drop across the part. If the current flowing is 250ma then the wattage being expended at that part is 250ma * 4V = 1W If you drop that part in Liquid N (Assuming it can operate at that temp) You would get a MUCH higher Wattage beause the heat wouldn't melt the part down. Current carrying capicity is really all about how much HEAT a part can handle or get rid of. High current parts are usually large because they need to sink more heat. -Mike
  7. Kirchoff was wrong, and by gum I'll prove it dome day! ;D -Mike
  8. Vcc refers to the voltage applied to the COLLECTOR of a transistor. Most commonly in digital electronics that is POSITVE. Vdd is the voltage applied to the Drain of a FET. The DRAIN is where the 'Holes' filled by electrons come from. It is positive (While electrons flow from negative to positive, In the HOLE theory, Holes flow from Positive to Negative. The ‘Hole’ theory was the accepted version of electronics flow before it was discovered that electrons were the moving entity and that they were negative. Both theories work equally well unless you mix them, I am an electron flow follower, so for me Diodes and transistors all point the wrong way but I just think of them as pointing toward the SOURCE of the flow not away from it.) Vss is the SOURCE of a FET that is where the Electrons come from. IT is Negative You may also see Vee. It is the Emitter of a Transistor, Usually referred to as Negative. These notations are normally used when marking integrated circuits or parts on data sheets. Some people also use them as a general indicator of POSITVE or NEGITIVE voltage on circuit diagrams. While this is not technically accurate as some of these circuits don’t even have a discrete transistor or FET in them. No one worries about it too much, we all just accept that in general (Vcc and Vdd are Positive and Vss and Vee are negative). There are situations where, for instance, the Vcc of a transistor will be connected to ground or even a negative supply voltage. It depends on what the function of the part is within the circuit. In general if you analyze that circuit you may find that even though it is connected funny, it is still functioning the same way it normally would. -Mike
  9. GREAT! ;D You and I can form a club. I feel the same way quite often. Actually I'll bet most of us* feel that way a lot. I work mostly with Communications and motor controls. I use mostly Z80,Amtel, and PIC chips in my digital work but I have used "Basic Stamps" when I was in a rush and they could handle the work load. My AC work focuses mostly on MOSFETs and Triacs depending on AC or DC. For small signal adjustment (Like boosting a small signal or trying to filter out a 60hz Hum) I use Op-Amps with active filters made of resistors and caps. I do use the 'Standards' when designing but I often find them lacking, but Like I said, they are common, cheap, and usually you have a few laying around. If I were to select a GRAB BAG of parts to take with me to a competition where I would be asked to build 'something' but not told what I would most likely take the following items: Proto-borad 7400 - Not gate 7401 - NAND Gate 74LS24x Series of latches LM741 Op amp LM555 timer LM556 Dual Timer Basic Stamp (Due to it's timple interface for programming) 7805 Regulator 7812 Regulator 7905 regulator 7912 regulator 1:1 audio Transformer 5:1 Power transfomer (1a @ 24Vac) A handful of 1n4001 diodes a few 5V Ziners a few 7v siners a few red/Green/yellow LEDS Resistors: 180, 470, 1K, 10K, 47K, 100K, 1M, 10M Caps: .001mfd, .01mfd, .22mfd, 1.0mfd, 10mfd, 100mfd, 1000mfd And Mi might throw a 100mh coil in the kit just for good measure. -Mike * US - Masters Of the Electronics Arts. Often beat themselves up over little things but they also get to feel the rush and excitement of acomplishment more often that normal folks!
  10. mostly black ones with lots of pins. ;D Seriously, what are you really looking for? I doubt that there is a "Most Commonly used chip" Schools are real heavy users of the 741 & 555 chips and the 3904 & 3906 BiPolars. Also the 1N4001 diode and the 7805 & 7812 regulators. Most textbooks cover those parts as the 'standards'. Just about every design I do requires a specialized chip, like an Opamp with a High Slew rate or a Dual timer (556) that runs at 3.3v. The 'Standards' may be good to test an Idea out but when it comes to actual building, I don't see a 'favorite' chip. In fact if I caught myself leaning on one chip too much I'd try to avoid using it for fear I was limiting my range. If I had to guess, I'd say the 74LS01/74HS01 is the most COMMONLY used chip in all digital systems. It is most definately the most used Gate in the world. -Mike
  11. Laptop PCBs are subject to a lot of twisting and bending. All the talk about 'Titanium cases' isn't to make the case harder to crush or protect it from dropping. The goal is to make the case as stiff as possible so the motherboard doesn't twist. Sony had a big problem with the PCB mounted memory because the sockets were so long and the board flexed enough to fatigue the solder joints. A retouch with a soldering Iron fixed most of the problems. You might also have a busted trace. A good pair of magnifying 'jewelers glasses' would be real useful in trying to spot the problem. A broken track will usually rip right at the edge of the solder mask. Look for a crack at the edge of the solder. If you see it you will need a steady hand and a needle OR a pointed exacto knife. Scrape off a little bit of the solder mask over the broken trace and then reflow the solder so it covers the exposed copper. This will make a stronger joint that should last. Just soldering to the edge of the ripped trace isn't enough. -Mike
  12. My guess is to search for the ECAWA Robotics Special Interest Group. I did a web search but found very little in the way of a place to BUY the board. You could try to find the designer, "J Fuller". A final option is to check with some place like 'Gecko Drives'. They make a 3 Axis stepper driver. They also make other motor controls. Hope that helps some! -Mike
  13. Yes, that would make it easier in many cases. :) Once in a while I have looked at a chip's pinout and wondered what the designer was thinking when they made the part. ??? Later as I started to design a board layout I found that some of the pin placements were rather clever. :D When working with a new chip with an odd pin out I try to find a example PCB layout from the manufacturer. These can sometimes hint at why some designs were selected. ;) -Mike
  14. In the US (My location) most consumer electronics are un-repairable. Actually you COULD fix them except for 2 problems: 1- The parts are usually very hard to find and sometimes can not be ordered in quantities less than 1000. 2 - The cost of paying someone to troubleshoot and then repair something is usually higher than buying a new unit and tossing the old one out. In the industrial sector there are different problems: 1 - Large companies that build and design electronics rarely have an in-house electronics design department unless all they build are circuit boards. Most often that work is outsourced. As there are many countries where labor is cheaper and Circuit designs can be easily transmitted over the internet. So there is not much demand for EE designers. 2 - The few EE's that are designing circuits are working at a very high level and have years of experience with a special system or company. Getting those jobs is difficult at best. All that remains are jobs where modules and equipment are connected together and configured. While a knowledge of electronics is helpful in this role, It hardly requires the ability to calculate phase shift or EMF interference. Most of the Tech schools (Some offer LESS than an associates degree!) provide 'Skilled' Tech workers who can learn to do much of this type work. As a result the job of being an actual working electronics engineer if trapped between board level swapping and Outsourced designs. In the end, Most EE's in the USA go into management and project work. Many take up a hobby that lets them use what they learned such as Ham Radio or Robotics. -Mike
  15. Output = (Input * Feedback loop resistance ) / Input resistance) On a clean OP-AMP with a linear response it’s all easy. If you have some harmonics, or your circuit has some frequencies that Drop out or resonate then the response will be a little harder to predict. However that is not a flaw with Feedback, it’s a flaw in the amplifier. (Or a feature depending on how you look at it.) -Mike
  16. Parallel ports are about as straight forward as you can get in the electronics world. 8 wires / 8 bits. Unless you need it to be complex try to keep it simple. Bi-directional ports can be done but some computers require you to Select that mode in the Cmos. Check your machine before you get Frustrated. Most ports support 8 output pins and 8 input pins (16 total) The 8 input pins are meant for the old line printers to use. (Paper out, Offline, Wait, Printer Ready, and some others….) These are often forgotten about because everyone goes right for The Bi Directional mode. If you only need a few inputs because You are building a controller rather than an input, try to use those. ALWAYS BUFFER YOUR INPUTS. Put in some sockets and put simple line buffer chips in as the first part for all the data and control lines. This will protect your computer from damage if you blow something on your board. NOT ENTIRELY but some protection is better than none!. BE CAREFUL ABOUT GROUND LOOPS. Make sure the ground on your PC is the same as your power supply. Some bench power supplies can be set to ‘float’ If yours does you will need a real solid ground between your PC and the PS. Use latch chips to capture data from the PC. If you try to latch the data at a Microcontroller you might miss the pulse. Remember your PC is running at a much higher speed than your Microcontroller. I don’t have any good Parallel examples because I have only built a few things that use the port. A CNC controller and a LED Sign. Later I wished I had used a serial port anyway. Good Luck! -Mike
  17. when it comes to line voltage in outlets I use a 'wiggy' that’s a brand name, I am sure there are other names for it. Electricians wouldn't be caught dead without one, In fact Without one, they might just get caught--- dead. A Multi Meter has a input resistance of about 20M ohms. This is great for low voltage but for home wiring it can lie to you. A WIGGY or similar device has a large AC electromagnet in it. When you place the WIGGY on a circuit (Like a multi meter.) the power from the mains causes the magnet to pull a little marker down to the line voltage it is detecting. (110,220,440 ect) The resistance of a Wiggy is about 200ohms this means that little stray voltages will not effect the reading. When doing a test of your grounds, Use both a high Ohm device like a multi meter and a low ohm device like a Wiggy to look for problems. If the Wiggy shows no voltage between 2 connections then it is safe to say that to CURRENT exists there, but in sensitive electronics that need a good 0V ground on a high impedance circuit there may still be some VOLTAGE on the line due to resistance in the ground wire and a ground fault further up the circuit.
  18. Gates is gates. TTL runs at 5vdc ONLY. Cmos can run at a wider range usually up to 15V and down to 3. You can mix TTL and CMOS at 5V. Most gates have 2 inputs and 1 output. They come in packages that have 14 pins usually. there are 2 power pins (Vcc and Gnd) The reaming pins are divided up (normally) among 4 devices (3 wires each * 4 = 12) These are called QUAD packages (Quad And, Quad OR) ect.. NOT gates only have 1 input and 1 output. In a 14 pin DIP there are 6 NOT gates. These are referred to as HEX parts (HEX NOT GATE) Using TTL voltages as an example: AND - if BOTH inputs are at 5V the output will also be 5V. it is 0v otherwise. OR - if BOTH inputs are at 0V the output will also be 0V. it is 5v otherwise. NOT - 5v IN give 0v out, 0v in gives 5v out. These are often combined so often that to same chip space manufactures made combo chips also. NAND - And gate with a NOT after it. Same as AND but the output is backwards. NOR - OR gate with NOT after it. Same as OR but the Output is backwards. There is one odd ball (isn't there always) called XOR or EXOR. This is just like an OR gate except that if BOTH inputs are high the output is low also. In other words: XOR - if both inputs are the same (5v or 0v) the output is 0v The method for figuring out how to connect the gates is called Boolean algebra. It also uses a lot of "Truth Tables" Truth Table: 1) list every input you want to measure across the top. 2) list every combination of on and off for all the inputs you provided. 3) At the end of the table create one more column called OUTPUT (or Q) 4) fill in that column with the desired results for each possible input. 5) hard part! Figure out what combination of gates will give you that result, Hint. Draw out the truth tables for ALL THE GATES and look for similarities. Send your truth table and I can show you some examples. -Mike
  19. Project management is the best part of being an EE? eeewwww. No the best part of life is when someone says, "We need to change this design to add a new feature that everyone says can't be done. We heard you were the best, can you do it?" and you get to say, "Yes." The second best part is when you get it to work and everyone thinks you are some amazing super human guru with alien knowledge that mortal humans can never possess. It's hard not to smile, All you did was follow some basic rules, draw on some experience and add a dash of creativity, yet from the outside looking in you get to be the hero. I like that part of the job the most. (I only get to do that OUTSIDE my day job because, Like I said, they don't pay well for that kind of work.) -Mike
  20. I wonder how r20552055 did with this project. Sounded like he was in a hurry. (Odd, PWM motor drivers are usually not a rush project.) Just my 2ma worth.. I have been building for a long time and I finally learned that there are times when it is faster and cheaper to BUY parts rather than build them. There are several good PWM motor drivers on the market from robotics, RC Cars, and industrial suppliers. Some as low as $20.00 US. If you understand how a PWM H-Bridge works, the 'Joy' of building one for yourself is lost on the project. If you just need to get it working, Buy the part from someone and plug it in. Concentrate on the bigger picture. I had a robotics project that was a killer with 6 Axis and I spent months designing and building (Etching, Soldering, resoldering) the driver boards and then more time tweeking the software for the drivers. When I added up the time and money I had spent, it would have been cheaper and faster to buy ready made parts. I would have had more time to work on the actual ROBOT. (The Fun Part!) -Mike ;D"Don't push me, I know how to Bias pentode screen , and I'm not affraid to do it!" ;D
  21. The RS232 standard uses 16V signals, however 12V is acceptable. The MAX232 chip uses 4 capacitors and some clever internal switching to convert a 5 volt supply into a 12V supply for the RS232 standard. Without the MAX chip you could use the 1466 Driver and the 1468 receiver plus a 12V power supply. Here is a little chart. I hope it aligns right. It shows the voltage levels we are talking about: 5volts (TTL level)---[MAX232 Chip]---(12/16V Rs232 Level) Tx from Microchip->TX In==TX OUT->Tx RS232 to PC. Rx To Microchip<-RX Out==RX In<-Rx RS232 From PC. Here is one solution you may look into as a simple test project. PIC 12CE684 (I think that’s the number) it’s an 8 pin part. It has 2 power pins (Vcc and Ground) It has 2 A/D converters on board (With an external Vref input if needed) And the remaining 4 pins can be used for anything else. You can pick 2 pins and make them the TX and RX pins for the serial port. The source code for the RS232 Protocol is on Microchip.com in an application note. Once you have the code modified to run on the PIC12 series, You can sample 2 different things at the same time and then send the data to a PC. I would have the PC send a signal to the PIC first, something like a ‘?’ symbol. Computer to PIC: ? Pic to Computer: 1=124<CR>2=209 Note: the PIC will return 0-255 from the A/D converter, you will have to convert that to an actual value your self depending on what you are measuring. For Instance if your Vref is 9v, then a measurement of 192 could be converted to a reading by (192 * 9) /255 = 6.78V (Binary reading times Vref) divided by Max Reading = Actual Value. Does that help? -Mike
  22. My Cynical Point of view: What they are not saying is that Electronics Engineering is a very odd field. I am an EE. I have yet to use so much as a Multimeter in my role because Most of my job is managing projects and PLC code review. I also Write code for desktops and manage a corporate Web site. I know a few other EE's who have similar roles. I build projects and fix stuff on the side for my own enjoyment. The days of an EE designing a new circuit or troubleshooting complex systems is long gone. Most EE's who are still doing that stuff are working in niche markets where they also have some specialized training in some other discipline. If you are getting into "Electronics" I'd suggest you do it as a hobby because it's rewarding, challenging, and fun. Plus it could lead you somewhere. If you need an income, I'd suggest mixing your electronics education with something like medical or Aerodynamics. People who have crossover skills get more money and are in demand. Diode jockeys are a dime a dozen now days. A few years ago trade schools chunked out millions of Electronics Associates degrees and employers found that they could hire EE-jr's for peanuts. As a result the 'Money' in EE moved to Corporate design labs, and project management. Both are not very enjoyable and neither are entry level positions. Be prepared to start off small and work up into a good paying job. For the entry level jobs slackjack posted, a majority of them are: Cable TV installer, Videogame/slot machine repair, Telephone equipment installer, Alarm Systems, PC bench tech(Swapping PCI cards and Hard drives) and Home entertainment system installers. The best Tech jobs I know of right now are Lan system engineers. Wireless and Business lan design is becoming a issue with small companies who need to move beyond the retail store switch gear and up into something more suitable for a large office. Learn how to set up firewalls routers, ISDN, Frame Really, and every other communications system. Then freelance for a while. Sell yourself. I have one friend who pulls in over 90K a year maintaining several businesses computer systems and Lans by himself. In the computer industry its all about certification. Don't waste time on an associates unless you plan on continuing to get a bachelors some day. Get certified in Cisco and Microsoft and you will find tons of work. Just my 2 cents and 0.04ma worth. Good Luck!! -Mike
  23. My personal choice is the Serial port. Parallel ports are getting rare on new machines and if you do use one you will need to run 8 data lines, 3 control lines (minimum) and you may have to fight the OS for direct hardware control of the port. USB is a very hard to use. It requires a complex protocol that is tricky to implement on a small system. The hardest part to manage is the memory stack needed. Most microcontrollers are limited in memory so just setting up a USB can be difficult. If you use a higher end processor or development board, some of them have built in USB support (The higher end PIC chips and the Rabbit systems for example) A serial port only needs 3 wires so the interface is physically simple. The Voltages can be converted using a MAX232 chip (Digikey part Number:MAX232ACPE-ND) This allows you to deal with simple 5V single supply systems. The Async Protocol is supported on many microcontrollers as part of the hardware. The PIC16,17, & 18 series all have UARTS and hardware support right on the chip. On the PC side the serial interface is easy to use also. Most OS actually handle much of the interface for you and they even supply terminal emulators. (Windows = Hyper term) In Visual Studio you can use the MSCOMM object for C or VB programs. With a baud rate of 192kbs the serial port is fast enough for most needs. -Mike
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