indulis

First, these to circuits are not exactly the same. They are however both 2nd order circuits. The professor is solving the system with state-space equations while the other solution is via differential equations. Since the circuits are different, why would you expect the solutions to be the same??

OK... say you go full wave. All that that will do is make the motor turn for as long as there is a signal in either polarity, provided it's "low" enough to turn on the PNP. In other words, signal = mouth open and, no signal = mouth closed. I would have thought the intent was to have motion to "loosely" mimic speech, and full wave WILL NOT ALLOW THAT!!! My guess would have been that motor was vibrating because it was being driven at to high a frequency, at which point, even if you had 100 A available, the current has very little to do with anything!!! You

Without taking into consideration the current needed to drive the motor, I don't see this circuit as being that bad, "for what it is", a cheap way to periodically activate a motor. Sure, with a servo you could get "movement" proportional to input amplitude, but the circuit isn't so simple anymore. Obviously this circuit is for unidirectional operation, and there is some other force applied to return the mechanism back to some predetermined position by either gravity or spring force. Is significant filtering of the rectified signal, or full wave rectification for that matter, from the transformer really needed? Wouldn't that just keep the motor "running" longer, thus defeating its periodic movement for the illusion of speech? I could see some "light" filtering with a time constant that is around the natural period of the motor being used, but not anymore than that.

Resonance with what? What is the other element, and how is it held constant?

A little off subject, but I have a question............. Obviously a speakers impedance isn't measured at DC. At what frequeny are speakers characterized for impedance??

To generate high flux, you need high current NOT high volts!!!!! I would think that this is an experiment where you want to keep the voltage as low as possible, but still be able to generate a high flux field!!!!!

The gap is not fixed.... can vary. Look at some gapped core data sheets, you will find something called inductance factor (nH/1000turns), typical numbers you'll see are 100, 160 and 250. Each of these has a different gap. To really understand this, and get a feel for how diffeent parameters interact, read a few articles on couple inductor design. The energy is stored in the flux in the gap.

Here you go................. https://www.surplussales.com/Wire-Cable/LitzWire.html In regards to: L2 RM10PA250-3F3 PHILIPS 10T PRIMARY LITZ(2X10X,1) 60T SECONDARY LITZ(1X15X,1) WINDING SEQUENCE (PRIM-10T, SEC-30T, PRIM-10T,SEC-30T, PRIM-10T) This is a coupled inductor. The core is a Ferroxcube RM10, with 3F3 core material, with an inductance factor of 250nH/1000T. 3F3 material is typically used from 100KHz to just over 1MHz, and avoid running it at more that 3000 gauss. The winding sequence is to maximize coupling and minimize leakage inductance. As for the winding sequence

Not always, the MPSA17 has a min V(br)EBO of 15V while a MPSH11 is 3V. The diode equation tells us that the "normal" P-N junction has a drift of ~2mV/

Wow.............. a 2F capacitor!!!!! It must have a VERY SMALL voltage rating (must be a hold-up cap of some kind). Keeping integration out of it, it all goes back to E=L*di/dt and i=C*dv/dt If the cap voltage is indeed low, the DC resistance of the coil will also have to be very low so it can draw LOT's of current to generate the flux field you want. The pulse would have to be relatively small as to not saturate the coil, and loose the field. If the the coil took the form of a air core solenoid, you could demonstrate the field strength by "launching" a projectile from it.

Ferrite core transformers sometimes do have a very small gap to prevent saturation and help in reset. In general, the idea with transformers is to NOT store any energy in the core. Leakage inductance, which all transformers have, will store energy in the core, so you want to minimize that with good inter-winding coupling and layer stack-up. Transformers also have copper & core losses. These relate to how big your winding window (how much copper of the best AWG can fit

More is not always better. There are dangers in making your cap's too large..... i.e. how would you limit inrush current? For the most part, the ripple is "more" a function of ESR. Most times cap's are put in parallel to get ESR down instead of capacitance up. Lower voltage cap will give you a higher capacitance in the same size package. Depending on the voltage levels, you might be able to use cap's from Oscon.... they are VERY, VERY GOOD in terms of low ESR!!!!!

Are you SURE you want to go with “that” (collector – emitter) or stick with the base - emitter junction?

If I understand correctly, you want to make a "universal input" (85 - 250 VAC ) adjustable switch mode power supply (0 to 30VDC @ 3A)… correct? This can be done, but the control loop is very, very tricky because of the wide swing in duty cycle and potential variation of the load!!! Take a look at some of the apps notes on the TI (formerly Unitrode) web-site.

You want to make a 4.6H air core inductor???

It's really ohms law at work. You have to consider the battery's internal resistance. You can hold the current constant and the voltage will go to whatever it has to, or hold the voltage constant and the current will be whatever it has to. Once you have defined 2 of the 3 terms, that's it. Switch mode converters do not like to run with light or no load. Depending on how you compensated the loop, the converter might go into a skip-cycle mode when lightly loaded and be stable, but it in all likelihood would go out of regulation. Or, it might just start to oscillate. If your running your flyback in continuous mode, you will be in trouble when you transition to discontinuous mode. Also, as a side note, current mode converters DO NOT have current limiting, they have power limiting. If you monitor the secondary current somehow (the average current, not peak), I suppose you could have a circuit connected to the TL431 reference pin divider network that would allow you to transition from constant voltage to constant current.

Since the "battery experts" themselves can't agree as to what is best, how can we determine which camp is "right"? I suppose one could argue that if the "pure DC" camp is correct, and since the vast majority of battery chargers are of the peak-pulse variety as opposed to the multi-stage DC type, the battery manufacturers have ensured themselves a long line of customers!! One of our sister divisions here at C&D Technologies makes batteries....... I'll have to see if I can get their postion/opinion.

Greetings Ante, From the www: Charging the lead-acid battery The charge algorithm for lead-acid batteries is similar to lithium-ion but differs from nickel-based chemistries in that voltage rather than current limiting is used. The charge time of a sealed lead-acid battery is 12-16 hours (up to 36 hours for larger capacity batteries). With higher charge currents and multi-stage charge methods, the charge time can be reduced to 10 hours or less. Lead-acid cannot be fully charged as quickly as nickel or lithium-based systems. It takes about 5 times as long to recharge a lead-acid battery to the same level as it does to discharge. On nickel-based batteries, this ration is 1:1, and roughly 1:2 on lithium-ion. A multi-stage charger first applies a constant current charge, raising the cell voltage to a preset voltage (Stage 1). Stage 1 takes about 5 hours and the battery is charged to 70%. During the topping charge in Stage 2 that follows, the charge current is gradually reduced as the cell is being saturated. The topping charge takes another 5 hours and is essential for the well being of the battery. If omitted, the battery would eventually lose the ability to accept a full charge. Full charge is attained after the voltage has reached the threshold and the current has dropped to 3% of the rated current or has leveled off. The final Stage 3 is the float charge, which compensates for the self-discharge. Much has been said about pulse charging lead-acid batteries. Some experts believe there is a benefit in reduced cell corrosion but manufacturers and service technicians are not in full agreement on the effectiveness. There are also disagreements on the "equalizing charge". An equalizing charge raises the battery voltage for several hours above that specified by the manufacturer. Although beneficial in reversing sulfation, the side effects are elevated temperature, gassing and loss of electrolyte if the service is not administered correctly. A periodic discharge of about 10% is said to benefit the battery but little conclusive evidence is available. In doing some research for questions posted on a few golf cart forums, I discovered there are also many misconceptions about lead acid batteries

A buck converter would be VERY hard to do!!! With a 5 volt output, and a nominal input of 110VDC that's a 4.5% duty cycle (plus a little for losses) and at 160VDC in it's 3.1%. Such small duty cycles are hard because of the speed at which you'd have to switch the swtching elements to keep the rest of the components relatively small. For a flyback, the leakage inductance spikes on the primary switching element could be a problem with a poorly wound coupled inductor.

One thing that will happen when using a 555 as PWM is that the switching frequency will change with line and load.

No, you can't current limit the ATX power supply by pulling on the standby pin, as was already stated. Pure DC is BEST for charging, it is too expensive to build/sell 20 or 30A pure DC chargers!!

None of those circuits can do 15A. If you look at the 1.2A & 2.5A chargers, there is a current sense resitor that turns on the NPN transistor connected to the "adj" pin. As the current goes up, the voltage across the resistor will increase until the NPN starts to turn on and pull down the adj pin. In this condition, the ouput current is controlling the output voltage. The LM317 itself has a internal current limit of 1.5 to 3.4 amps when Vin - Vout is 15V or less. Not very exact!!!

Can you be a little more specific about the 110VDC input voltage? Is it a "nominal" 100VDC with

What you just said is pretty much what I meant. You need circuit that can operate in voltage mode and current mode, basically voltage foldback. Under certain conditions you want the output voltage to control the output current, and under other conditions you want the output current to be able to control the output voltage. At the same time you need to make sure the output current will never be more than 15A. Those

OK...... so what your "saying" is that, in a second order Butterworth low pass filter, there is gain just prior to the corner frequency due to "positive feedback"??? The transfer function only has poles and NO zeros, how can that be???