Theatronics

Buy a DVM. They cost between 20 and 100. IF you want to BUILD such an beastie you need several parts. (Dozens) and some skill with a microprocessor or a custom DVM chip. Cheaper and faster just to buy the DVM. -Mike

Thank you to all the moderators. Your efforts are not being over looked. Good luck in your spam battles! -Mike

Did I mention arc Flash? ;D Yea, getting a High voltage DC from a High voltage AC is a bit of an odditty. Usually if you want a High voltage you are not working with electronics so much as you are working in physics. Particle accelerators, Tesla Coils, Beam and ray generators. These all fit under the 'Crazy uncle Bubba' catagory of home hobby technology. Once you do have that much DC voltage I can't think of too many things to do with it. It's hard to contain, there are few devices that can handle let alone modifiy it and you can't even convert it back down to a lower voltage because it won't go through a transformer anymore. Humm, This only thing I can see doing with that much DC is to discharge it through some sort of equipment that needs high EMF to break down a dielectric barrier. Who knows maybe he is building the first 50KV PNP transistor. you know, three carbon rods fused into a silicon glass orb maybe? I always wanted to build a fish tank sized Triode for a science fair project, I could not evacuate a fish tank enough though, the glass cracked. I guess I could ahve put pyrex supports inside but hey, Live and learn. -Mike

It seems my dry wit is lost on this board. ::) My selection of the 1N4001 was meant to be funny and informative. The 4001 is arguably the most common diode in electronics. I used the most common element to demonstrate the method of Stacking diodes to get higher voltage ratings. Sure I could have used a much higher value diode but where Would be the humor in that ? At the end I did suggest (And even showed a picture of) high value Diodes that could be used but that didn't seem in the spirit of the question. The ‘One Part’ answer is something like the BR412-50-xx (Where xx is 5,10, or 25 for the number of MilliAmps you want) It’s about 5 inches long and 1/4in Dia. Made by a company called ‘EDAL Industries’ Located in East Haven, Connecticut. USA. Their phone number is (203) 467-2591 They do have a web site but no way to buy Product online. I have yet to locate a distributor. I don’t know the cost of the unit but I’ll bet it’s Not cheap. To be fair, Nametc3 did say he wanted to ‘MAKE’ a HV rectifier Not buy one. So Nah. :P Now I have to go back to popping 10ga wires like little fuses, Can you say 'Arc Flash explosion?' Weeeee -Mike

Does he mean the upgrade for the horses? I think it can only be installed at the factory. -Mike

I know how to take Medium voltage AC and turn it into high voltage DC. the circuit is called a Cockroft Walton Voltage Multiplier. Build a HV Rectifier? Hummm. Lets see, at 50V max breakdown per diode, it would take a stack of at least 1000 1N4001 diodes in series (with a loss of 1100 volts loss in forward Knee voltages) to turn 50Kv ac into 50KV DC. Of course you would be limited to 1 Amp current and you would need a HECK of a capacitor stack to smooth out that ripple. But hey, in bulk 1000 diodes only costs $40.00 us. Humm The lead free solder to string them all together might cost more though. I am sure there are much higher rated diodes out there but you get the idea. Find a 10KV diode and you will only need 5 of them. Here is a picture from A surplus site of a 5kv Diode. They cost about $35.00 used. (Surplus Sales.com) -Mike

I am guessing that ‘M/C’ means Motor Control. It also sounds like you are dealing with 3 phase Power so the motor control you are talking about Must be a fairly hefty one. What concerns me is not the 30A rating of The controller but the current demand of the Motors you plan on using. At 220V with 7A You can expect around 3-4 Hp or 1500W (Note: I just rounded, I did not compensate for 3 phases or power balancing) If the motor is under that range then you should not have a problem The transformer can only provide up to 14 amps max, and if the Motors only draw 14A max then the 30 rating of the controller Should be a blessing as it can easily handle the load. The one thing that you did not make clear is the type of Transformer you have. I am guessing you have a step down Transformer to drop from 415 down to 220. I have not encountered A large number of 3phase transformers that make such a small Step. Usually I see 13,800V down to 220. I was worried that you Had a single phase transformer and you wanted to get 3 phase Power from it.

I work with AGV’s a lot. They have many ways of finding themselves and one of them is quite easy to set up. If you place 2 or 3 beacons around your driveway you can set up a nice system that will be fairly accurate. The system works like this. Beacon 1 sends out a 10khz IR signal. Beacon 1 sends out a 20khz IR signal. Beacon 1 sends out a 30khz IR signal. Or any method that you find easy to set up. On each car there needs to be a rotating mirror That shines the beacon lights down (up?) onto A sensor. (Look at an old rotating police lamp to see how) The sensor is amplified then fed to 3 signal detectors. (Or more if you need more beacons) Each one outputs a pulse when it detects its signal. (A signals Beacon 1) (B signals Beacon 2) (C Signals Beacon 3) Ect.. for more if needed. The last thing you need is a high speed timer. The faster you motor spins the faster your timer needs to be. You will need a sensor on the motor to detect 1 revolution. When the motor makes contact with the sensor to signal the start of a rotation, The timer starts. As the mirror spins, when a signal comes in the value of the timer Is copied into a register. When the Motor makes contact with the Shaft sensor again the timer is stopped and copied into a 4th register that is used to calculate the time for 1 full turn (360*) Then by looking at the 4 registers you now can calculate the angle between the car And the 3 beacons. If the Shaft ZERO point is aligned with the axis of the car then You can say that the signal from Beacon B is 25% of the full time for 1 rev. therefore it is 90 Degrees off center. Beacon A is 40% of the full time and therefore is 144 degrees off center, and Beacon C is 83% of the full time for 1 rev. therefore it is 298 Degrees off center. Given these three angular measurements you can calculate the position of the Car relative to a known stored position (Home base) or in relation to the known positions of the towers. The process is actually called “Trilateration” . It is not dependant on the time delays of a signal or a known measurement as much as it is a relative measurement of a known point and the differences. It’s not super Easy to do, but it is another way to make it work. This method works best if the car stops and takes a reading once and a while. While it can work ‘ON THE FLY’ the spinner needs to be very fast and that requires a super fast processor. -Mike

I would guess that is is a rare custom chip. It could be a common part, but my experance has been that devices like that often are built around a custom part or one where they scratched the part number off the top. One way to be sure would be to use some solder wick and just desolder the gauge and take a look at the chip. If there is a part number we might just be able to find a Data sheet. I am guessing it is something like this: http://www.national.com/pf/LM/LM2917.html But it could easily be a small microcontroller that has an onboard signal counter and a PWM output driving the gauge. -Mike

The human eye can only detect flickering up to about 40hz at max. Above 100hz and humans see only a solid light. (Neon and Vapor lights flicker at 60hz) LED's can flash on and off MUCH MUCH faster, thousands of times a second. Set up a LED flasher that flashes the LEDs at 1000hz. Then control the 'Apparent' brightness with the duty cycle of the on cycle. If the LED's are only on 1% of each cycle they will 'Appear' very dim. if they are on 99% of the cycle they will 'Appear' very bright. LEDs were designed to work at one voltage. While some PN effect fails due to manufacturing errors thus allowing them to dim a little at lower voltages. A perfect LED would hardly light at anything below it's Knee Voltage. Too much voltage and the current melts the die. Pulse Width is the key. -Mike

What ever one your skip, I suggest you take it next semester. OptoElectronics is exciting because of the changes in LED technology that have taken place over the last 5 years. New colors, Higher outputs, and even Laser outputs. Also the High switching speeds has pushed the network communications even higher. This can be an exciting field but I am guessing they will only cover the basics if you are only taking 1 semester of it. Embedded systems sounds like a microcontroller class. This class will focus on complete modules that have functions all their own and how you interface to them in larger designs or circuits. My choice would be the Embedded systems first as Opto is moving so fast, next year there will be new things to learn so I’d rather let that technology grow as long as I can before I jumped in. In the end I’d still want to take both. -Mike

Vi Wh Bl Rd - Gr 7 9 6 2 5% 796 * 100 =79600 Rd Yl Or - Gld 2 4 3 10% 24 * 1000 =24000 Vi Bl Vi Br - Gr 7 6 7 1 5% 767 * 10 =7670 Vi Wh Bk Rd - Gr 7 9 0 2 5% 790 * 100 =79000 Those switches can be tricky on the inside. Some have been set up to short multiple contacts and create unexpected outputs. Others are just straight forward 3 position switches. In any case it appears that the resistance is used to control the measurement. That trim resistor on the side looks very promising. The shadow and the parts placement make it hard to follow the traces. It appears like there is a chip under the gauge and the gauge has 2 large pins that straddle the chip. I would try and work out the circuit diagram of at least the switch the chip and the gauge. The other parts may be just power regulation. Once we understand how the switch works to provide resistance to the chip I think we will find that the number of calendars Vs. Revolutions per a second is a simple formula and by replacing some resistors we can do 2, 4, 16 or 24 calendars just by putting the correct resistor on the board. -Mike

Hey , I'm an electronics geek, not a motor head. Sheshh. Yes I forgot that in ICE's that there needs to be an exhaust cycle for each piston. That would equate to 2 revs for 8 firings in a 8 cylinder engine. That just means we need to divide (or multiply) by 2. Eh. Not so hard. What is the pickup or signal input method on the tachometer? Inductive pickup, Direct wiring? Is there a sensor on the crankshaft? -Mike

SORRY! See what happens if you don't get your morning caffene! I thought that you were asking about FBGA (Ball Grid Arrays) (Field Programmable GATE arrays) Ohhhh. well that’s something different. They usually require a (Compiler) that will take a logic formula or some even use graphical diagrams, and convert it into a series of signals that (open or close) connections between prewired gates in the chip) Depending on the device used, there the programming interface can range from an In-Circuit programming, A standard EEprom Burner, or a custom interface. I have used devices from this co before: http://www.xilinx.com/ Sorry about the confusion -Mike

FPGA means (Flat Pack Grid Array) This is a package type, not a chip type. Programing will depend on what electronics are in the FPGA. Do you have a part number? -Mike

Voice activated without recognizing a voice? Ok, why not. I am going to assume you mean that if you say (OPEN) The door will open for a while and then close again. You might also want to add ‘CLOSE’ later but that is More complex. What you are looking for, I think, is a sound activated circuit. The sound of a voice would be the trigger. The key of course is to select some attribute of the voice that is unique Enough that the door will not trigger to just any word or sound. In English ‘OPEN’ is a long vowel sound with a hard percussion ‘P’ in the middle, and then a soft ‘nnnnn’ sound. Looking at a scope and a frequency range there are 3 distinct events. You could do something like this. Set up a series of notch pass filters, similar to a graphic EQ. Then say the word ‘OPEN” several times and tune the notches so that they switch on and off as you say the word and different frequencies are accented and muted. Have the outputs light LEDs for testing. Then feed the outputs into series of logic gates (And gates) Lets say you end up with 5 notch filters. Named (a,b,c,d and e) O triggers a,b,c, and e Ph triggers all of them En triggers c,d and e Then set up your logic thus: Key 1 = A and B and C and E and not D Key 2 = A and B and C and D and E Key 3 = C and D and E and not A and Not B Then a sequential circuit can be set up where the Keys need to be triggered In the proper sequence in order to get the system to output a signal. (A series of flipflops would work) Personally I would use something like this: http://www.sensoryinc.com/ This device has VR built into it and is easy to set up. You can have it Open, Close, Lock , Unlock and ring the door bell and still have space left over. Good Luck -Mike

That would be called a GEAR MOTOR. It will have a reduction gear on it that produces the slow speed and high torque. Try 'GRAINGER.COM' or http://www.robotmarketplace.com/marketplace_gearmotors.html At least then you will know what you are looking for. -Mike

Need to know more. What are the values of the resistors you mentioned. What kind of display does it have, sounds like an old moving needle? Can you measure the signal going into the needle display? (is it a DC voltage that varies or maybe PWM signal?) Normally the way a tac works is it measures the number of firings that occur on the main coil. The distributor cap then diverts each spark to a different sparkplug. So if there are 8 sparkplugs, divide the number of sparks by 8 and you have 1 rotation of the engine. For a pure analogue method, I suppose you could take the number of pulses coming in, amplify them by a fixed amount (controlled by a resistor on a n op-amp) and then feed the result into a capacitor. Much like a switching power supply. the stronger and for frequent the pulses are, the higher the output voltage from the cap will be. Feed that signal to a calibrated voltmeter and presto you have a tac. I am guessing that the resistors are the feedback resistors on a OP-AMP. You might try installing a variable resistor in place of one of them and then hook the unit up to a 4 cyl car. Using some other device measure the rpms of the engine and then tune the variable resistor down to get the correct reading. Disconnect the resistor and measure it to see what the resistance is. Then match that as closely as you can with standard values. If you want, you can just leave the VR in but use a 15 turn PCB unit and glue the screw when you get it right. Otherwise it may turn and come out of calibration. I could be totally wrong because we don't know enough about the unit you are using yet. -Mike

I don't have a schematic but I can give you a hint. The modules usually transmit a 38-40khz signal. the transmitter is just an IR led and the receiver is a IR sensitive Photo transistor. An amp and a Phase Locked Loop pick up the signal from the transmitter. The data being sent is transmitted at a very low frequency. If you send on/off pulses too fast you will begin having trouble with the carrier freq (38-40khz) When set up correctly, a high signal into the transmitter will begin sending the high freq IR signal through the LED. The receiver will pick it up and output a high signal because the PLL matches the signal being sent. Turn off the transmitter and the output of the receiver also goes low. Hope that helps. -Mike

You may have broken down your solution the wrong way. Lets look at the rules: 1) Sample the Air only if the fan has been off for 30 seconds or more. 2) When signaled, switch on the fan for 30 seconds than shut it off. It sounds like there is a definite ladder logic to this. You might want to look At a device called an IDEC Smart Relay. VERY easy to program (There are only about 8 commands and they are mostly delay timers and logic gates) They run 110Vac or 12/24Vdc with 4 relay outputs and 6 Inputs they are very handy. It will save you TONS of circuit development time. If you want to DIY then I’d suggest something like this. -Mike

WHile you can get nearly a 50% duty cycle out of a 555 with a little work, it is easier to use a flip-flop to do the work for you. If you want a 30 second on and a 30 second off: Set the 555 timer to pulse once every 30 seconds. it doesn't matter what the duty cycle of the pulse is. Run the output of the 555 to a 74LS74 or equivliant chip. (30sec pulses into pin 3) (Tie Pin 2 to pin 6) (Perfect 30second ON, 30Second Off pulses out of Pin 5) (14 is +5v , 7 is gnd) is that helpful? -Mike

What do you need to know? -Mike

The 'COLD HEAT' soldering iron works on the tiny amount of current needed to heat the element at the end of the device. Look closely at the end of the tip. It has a divide down the middle. Both sides of the tip must touch a conductor. The current flowing through the conductor will cause it to heat very quickly. On the Top of the device is an LED that should turn RED when the tip is in contact with a good conductor. AS the heat builds you can then add solder. On the TV ad they show people (ZAPPING) things together. In fact that is a BAD thing to do because the solder and metal have not had a chance to 'FLOW' and as a result you will get a cold solder joint. Leave the device ON the part for a moment and then add the solder. Just like you would with a normal soldering iron. The tip REALLY DOES cool down as fast as they say. So I do like using mine. I have a few butane irons I have used also but the heat from the flame on the side of the units melt and burn nearby parts. The "COLD HEAT' unit has some good uses but it is not a universal tool. Important tip. Never heat the SOLDER. as the solder melts the electrical contact will break and it will be hard to keep the heat flowing. Remember it cools down VERY fast. Heat the PART then add the solder to the PART not the tip. Let me know if that helps. -Mike

BJT's are current devices, they use the flow of electronics through the PN junction to create a cascade effect allowing a larger current to flow from Vcc to Vee. Because the flow is proportional, a small current at the Base can control a large current at the collector. (And Emitter if you look at it that way) FETS (Field effect Transistors) use VOLTAGE as the controlling agent. As a result the actual Current flow is limited because in essence you are putting current into the fet at the PN junction backwards. It acts like a backwards diode so only a tiny current will leak through. The MOS (Metal Oxide Silicon) FET enhances this by adding a layer of GLASS to the mix. The glass isolates the gate from the Source and Drain. In effect there is (Ideally) No current flow at the gate, Only voltage. Just like a capacitor pulls a charge across an insulator (Dielectric) the Fet causes a static charge around the Gate. Because the current in the device needs to flow past the gate the static charge on the gate acts like a clogged pipe and restricts the flow. As this charge builds it begins to PINCH OFF the current flow through the Drain-Source pathway. It is a lot like stepping on a garden hose. While you are not directly adding any water to the flow, you can 'pinch off the flow' through the insulator of the hose. The voltage required to totally shut off a FET is called the Pinch Off voltage. Some FETs (Enhancement and Depletion mode) are OFF until a voltage is applied to the gate. They work on the same concept but there are extra layers to the FET making it more complex, Without getting into the would junction theory of how it works, Just think of them as working BACKWARDS. The More VOLTS applied, the more OPEN the channel is. does that Help ? -Mike

Just in case you wondered. The inside of a 7805 looks like this. (Sort of). Depends on the manufacturer. -Mike