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  • -max- commented on mchau2's forum topic Which arduino borad to buy?14 hours ago

    You don't necessarily need a lot of pins. Shift registers allow converting a serial data stream into several outputs. Of course you are literally trading speed for pins, but if you are just running LEDs as indicators, there is no problem.-One thing I have to point out against the MEGA and non-ATmega328 boards is that some of the code you find is written to work on the most common arduino UNO, or 328 chip. Things like using PORTX commands instead of digitalWrite, which complicates the more advanced projects, as you need to be aware of the MEGA pinout.

    I personally like the MEGA because not only you have more pins, but also more programming space, and I want to say it's faster too. It enables complex designs requiring many UART ports, interrupts, PWM and analog pins, etc.-The arduino Due is also nice, ARM based, but has 'quirks' that differentiate it from the rest. It's faster due to 32 bit arm microprocessor. It's 3v3 logic, so be careful. It's more sensitive to stuff like that. It also offers some real DACs if I recall right.-If you get an UNO, avoid the ones without replaceable chips. Those are IMHO garbage. Get the ones with the full DIP package on them, because if you fry it, then no worries, a $4 replacement chip will almost certainly fix it. And it allows you to program any chip you want and then install it into a final project...see more »I personally like the MEGA because not only you have more pins, but also more programming space, and I want to say it's faster too. It enables complex designs requiring many UART ports, interrupts, PWM and analog pins, etc.-The arduino Due is also nice, ARM based, but has 'quirks' that differentiate it from the rest. It's faster due to 32 bit arm microprocessor. It's 3v3 logic, so be careful. It's more sensitive to stuff like that. It also offers some real DACs if I recall right.-If you get an UNO, avoid the ones without replaceable chips. Those are IMHO garbage. Get the ones with the full DIP package on them, because if you fry it, then no worries, a $4 replacement chip will almost certainly fix it. And it allows you to program any chip you want and then install it into a final project easily.-If you are really clumsy, get the ruggeduino. Every input has protection, and the board is (almost) bulletproof.-Lastly, I like the tiny breadboard arduino pro's. They are just a jellybean arduino with the typical standard ATmega328, no thrills. But they are small and great for smaller projects where price and size are a concern. I bought 5 clone boards for $15.

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  • -max- commented on -max-'s instructable Easy SSTC, Slayer Exciter On Steroids!2 days ago
    Easy SSTC, Slayer Exciter On Steroids!

    You should totally refer to my youtube tutorial and ask there! ;)..jk. Assuming you tried everything in the tutorial section (DO THIS PLEASE) then there is a good chance your MOSFETs are dead or your driver is dead. Build up a basic test circuits and troubleshoot each component. Silicon tends to fail easily, so diodes, transistors, chips, etc.Plenty of tutorials of how to test transistors and MOSFETs, The DS0026 or equivalent chip should produce an inverted output on an osciloscope compared to the input. The output should be able to drive a load with static voltages present on the input.-You should have a read through this to understand why parallel MOSFETs is NOT a good idea if you don't know what you're doing.http://www.irf.com/technical-info/appnotes/an-941....Basically the gist is t...see more »You should totally refer to my youtube tutorial and ask there! ;)..jk. Assuming you tried everything in the tutorial section (DO THIS PLEASE) then there is a good chance your MOSFETs are dead or your driver is dead. Build up a basic test circuits and troubleshoot each component. Silicon tends to fail easily, so diodes, transistors, chips, etc.Plenty of tutorials of how to test transistors and MOSFETs, The DS0026 or equivalent chip should produce an inverted output on an osciloscope compared to the input. The output should be able to drive a load with static voltages present on the input.-You should have a read through this to understand why parallel MOSFETs is NOT a good idea if you don't know what you're doing.http://www.irf.com/technical-info/appnotes/an-941....Basically the gist is that because no 2 MOSFETs are identical, one will conduct way more current than the other when ON and especially in the linear region of operation. You need current sharing resistors on their drain and gate for reasons explained in that application note.---------------p.s. If you plan to do much more electronics you gotta learn to read up on this stuff! It can get intense, I know. Look into picking up a copy of the Art of Electronics. It has almost everything you would need to know in it!

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  • Make the simplest adjustable power supply in 10-15 minutes!

    So then my original point holds true. To truly figure out how much power a regulator can dissipate, you need to do some basic thermal calculations. Different case styles have different thermal resistances. (goto comment 1)TO220 is typically just under 1 *C/W, from the silicon chip inside to the case. If you let the package stand in free air its about 35 *C/W from junction to ambient, depending on air flow.Exceed the thermal and you ARE abusing the part. Thermal cutoff typically occurs at 150*C which is too hot. 100*C is the max for reliable operation

    My original comment was simply adding to what you said (apologies if that was mistaken to be a correction), then you argued that you can ballpark it for many applications, which I agree with for typical non-critical DIY projects (particularly when breadboarding and having access to a reasonable size heatsink), but that does not make it good practice. A linear regulator is most often (almost always) limited by thermal dissipation capability, at least in my experience. Sometimes a power derating curve is offered by the datasheet, but this is basically just power dissipation limits calculated for you.I tried to stick a 7805 inside of a small LCD module which was drawing 350mA at 5V. Powered from a 12V RC battery. While on the breadboard mounted on a small heatsink it got a little warm but ...see more »My original comment was simply adding to what you said (apologies if that was mistaken to be a correction), then you argued that you can ballpark it for many applications, which I agree with for typical non-critical DIY projects (particularly when breadboarding and having access to a reasonable size heatsink), but that does not make it good practice. A linear regulator is most often (almost always) limited by thermal dissipation capability, at least in my experience. Sometimes a power derating curve is offered by the datasheet, but this is basically just power dissipation limits calculated for you.I tried to stick a 7805 inside of a small LCD module which was drawing 350mA at 5V. Powered from a 12V RC battery. While on the breadboard mounted on a small heatsink it got a little warm but not bad. However once assembled the regulator overheated, melted the inside of the case, cause LCD clouding (thermal heat damage) and the regulator died. It was not even close to the rated 5A but I neglected power dissipation inside a plastic case with no ventilation. It was dissipating over 2W of heat.I know linear regulators inside out (Literally!!!), as I have built many linear regs from BJTs on multiple occasions. I am working on a really nice 14 bit microcontroller lab bench power supply capable of 0 -- 5A; 0 --15V. I not have a "beta" build working on a perf-board to improve performance and reduce the changes of marginal instability. I plan to use LT1007's in the final design for the low noise, lower voltage offset, higher precision, and MUCH higher slew rate. Only thing that needs to be done is to layout a proper PCB and figure out frequency compensation components.

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  • building the poor-mans mini tesla coil ( slayer exciter)

    Sure, I'd love to see the performance. But does it compare to my MOSFET based SSTC? ;)It is probably worth noting that darlingtons are not the best for high speed switching, as the case with this 1MHz oscillator. A 100 -- 1k resistor between the emitter of the first transistor (also the base of the 2nd) and the emitter will should help improve performance.

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  • I recently made a basic crystal radio using a SOT-23 packaged schottky diode salvaged from an old PCI RF TV tuner. Vd = 0.25v on multimeter. It was part of a small local switching regulator.

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  • Make the simplest adjustable power supply in 10-15 minutes!

    Many voltage regulators have protection mechinisms in place, sure. That does not mean you should be careless about how you treat them, I have had many regulators die from abuse from heat and short circuits. They are not fool proof.By "junction", I am referring to the primary pass transistor inside that is the culprit of all the heat.

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  • Make the simplest adjustable power supply in 10-15 minutes!

    The datasheet can give you the maximum power dissipation, and that is generally assuming you can keep the case of the package at room temperature, and the junctions will be at the maximum temperature (150*C) Of course in the real world it is almost impossible to achieve like 100W of dissipation while keeping the transistor at 25*C w/o an active heat pump.

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  • building the poor-mans mini tesla coil ( slayer exciter)

    Not a good choice, but it might work. Look at using medium power transistor with a high voltage rating and a high current rating, and good gain.

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  • -max- commented on spark light's instructable Building a solid state tesla coil1 month ago
    Building a solid state tesla coil

    Imagine 2 bully kids pushing a kid real hard back and forth on a swingset, each pushing at just the right time to get the kid swinging very VERY fast!That... is this.

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  • building the poor-mans mini tesla coil ( slayer exciter)

    Refer to the troubleshooting step for the small version. I think you will find the answer there.

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  • -max- commented on Yergaderga's instructable Creating Alternating current1 month ago
    Creating Alternating current

    Relays can very easily be configured to self oscillate, simply by either connecting the normally open contacts directly parallel with the coil, and having a lamp in series with the coil powered from a source, OR by connecting normally closed contacts in series with a coil, and connecting that to power.You will have high voltage spikes across the coil, and could get a nice tickle-shock from it, probably enough to startle you or blow a multimeter up, both of which I did.The contacts will also wear out very quickly as an arc is drawn when the contacts come apart. I have caused a 50A car relay to melt in this way, and destroyed many smaller ones in seconds. I also used a refined version of this self-oscillating setup to drive and test ignition coils, with great success and 1 inch sparks fro...see more »Relays can very easily be configured to self oscillate, simply by either connecting the normally open contacts directly parallel with the coil, and having a lamp in series with the coil powered from a source, OR by connecting normally closed contacts in series with a coil, and connecting that to power.You will have high voltage spikes across the coil, and could get a nice tickle-shock from it, probably enough to startle you or blow a multimeter up, both of which I did.The contacts will also wear out very quickly as an arc is drawn when the contacts come apart. I have caused a 50A car relay to melt in this way, and destroyed many smaller ones in seconds. I also used a refined version of this self-oscillating setup to drive and test ignition coils, with great success and 1 inch sparks from a 12V drill battery.

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  • building the poor-mans mini tesla coil ( slayer exciter)

    I have troubleshooting tips on the last few steps. If those do not work then ask again. Good luck.

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  • building the poor-mans mini tesla coil ( slayer exciter)

    This circuit took me weeks to perfect. It's hard to tune due to the chaotic nature of its operation. Take a look at my last few steps for troubleshooting.

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  • -max- commented on -max-'s instructable Easy SSTC, Slayer Exciter On Steroids!5 months ago
    Easy SSTC, Slayer Exciter On Steroids!

    You can also alternatively try making your own MOSFET buffer driver with a couple of transistors. Use 2 (a NPN and PNP) transistors in the emitter follower configuration with the base's connected together and the emitters connected together. The emitters go to the MOSFET gate, and the base is fed from the feedback pin. Due to the nature of PNP and NPN transistors, protection diodes are not critically necessary, as the PN junctions will do the trick. The transistors are acting as emitter followers, so the NPN collector is connected to Vcc and the collector of the PNP is connected to ground.

    It's hard to say, I killed all my DS0026's working with this circuit, too. And I have no plan to buy them. (I only used that chip because I had them in my antique junk bins.) Look up the datasheet and have a glance at the Absolute Maximum Ratings for your device, it will list all the things that, if you exceed, will result in the magic smoke.

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