Using mosfets is generally recommended for anything outside of power audio since you don't have to worry about base current, since you're using a transformer the mosfets don't need to be high voltage rated so they should be pretty cheap.
If you're having trouble finding a matched P-channel mosfet I recommend the quasi complementary driver configuration which let's you use two N-channel.
If you don't know what I'm talking about, using a single transistor to switch V+ through a transformer gives very poor performance, you'd be lucky to manage 5W output, instead you should be using a push-pull driver configuration.
[QUOTE=Nikita;41150155]Hey guys, I want to build a battery-run 12 VDC to 110 VAC inverter for about 30W of power.
Can I use MOSFETS to generate the 0, +6, +12 voltages to feed into transformer, or does something like that require BJT's?
Do such things usually catch on fire or kill anyone?[/QUOTE]
[url]http://translate.google.com/translate?u=http%3A%2F%2Ftechmind.dk%2Farduino-singleboard%2Finverter-12v-dc-til-230-volt-ac-med-arduino%2F&hl=en&langpair=auto|en&tbb=1&ie=UTF-8[/url]
[url]http://translate.google.com/translate?u=http%3A%2F%2Ftechmind.dk%2Farduino-singleboard%2Finverter-12-volt-til-230-volt-med-arduino-version-1-1%2F&hl=en&langpair=auto|en&tbb=1&ie=UTF-8[/url]
I want to repurpose some old harddrives as motors. Anyone know the best way to go about driving them?
[QUOTE=SEKCobra;41155891]I want to repurpose some old harddrives as motors. Anyone know the best way to go about driving them?[/QUOTE]
Here is a quick and easy way to get them running:
[img]http://forums.parallax.com/attachment.php?attachmentid=67697&d=1266079979[/img]
[url]http://forums.parallax.com/showthread.php/119874-Hard-Drive-Stepper-Motor-with-high-speed-spin-up-circuit?p=88128%C2%AD5#post88128%C2%AD5[/url]
It's not the best way to drive them however since you have to spin it up manually.
And they get rather hot quickly.
Also harddrive motors give very little torque.
[QUOTE=Chryseus;41150630]Using mosfets is generally recommended for anything outside of power audio since you don't have to worry about base current, since you're using a transformer the mosfets don't need to be high voltage rated so they should be pretty cheap.
If you're having trouble finding a matched P-channel mosfet I recommend the quasi complementary driver configuration which let's you use two N-channel.
If you don't know what I'm talking about, using a single transistor to switch V+ through a transformer gives very poor performance, you'd be lucky to manage 5W output, instead you should be using a push-pull driver configuration.[/QUOTE]
Oh, okay, thanks!
[QUOTE=Chryseus;41157058]And they get rather hot quickly.
Also harddrive motors give very little torque.[/QUOTE]
Well it should be fine at the rated speed and with low ballast.
After spending weeks slowly moving into this new room I finally got my desk in a reasonably finished and presentable state;
[img]http://puu.sh/3mZaJ.jpg[/img]
The reason for the height difference of the benches is because when doing electronics stuff I tend to want what I'm working on closer to my face so I don't have to bend my back. Though if ever I change my mind I can just shorten the legs.
I've yet to put up all the shelves and that monitor on the floor in the bottom left will fill the gap on the pc bench once I get another wall mounting arm. Plus I've got a couple of HP bench meters and a beefy switchmode lab supply that I need to repair that will join the rest of the EE gear.
Hang your cables and test leads on hooks on the wall. It looks a but akward storing them in boxes.
[QUOTE=pentium;41162927]Hang your cables and test leads on hooks on the wall. It looks a but akward storing them in boxes.[/QUOTE]
There's not a ton of wall available to hang it on that's nearby but I am planning to make a hanger that goes on the side of those parts cabinets. Not gonna have a huge capacity but if I can just hang some of the most frequently used ones that'll be fine. I also have a wire spool hanger in the works.
I feel like getting into FPGA programming, it seems different and fun for once
I found this: [URL]http://www.wayengineer.com/index.php?main_page=product_info&products_id=161[/URL]
Its cheap since I dont have much dosh on me right now (well I do but I'm a cheap fuck)
I sadly cant find any info on programming it, it probably needs some proprietrary JTAG crap
[editline]24th June 2013[/editline]
From the same site, this also looks p good, actually much better: [URL]http://www.wayengineer.com/index.php?main_page=product_info&cPath=50_55&products_id=2235[/URL]
Look at what the postman brought today
[img]http://puu.sh/3ncjB.jpg[/img]
I bought and built an FM transmitter kit, but I accidentally powered it with 9 V instead of the 6 V required. Did I fry something?
Schematic:
[IMG]http://i.imgur.com/zgYlxKt.jpg[/IMG]
Transistor (S9018) datasheet:
[url]http://gmicroelec.com/userfiles/product/1322460088395.pdf[/url]
[QUOTE=Val67;41167952]I bought and built an FM transmitter kit, but I accidentally powered it with 9 V instead of the 6 V required. Did I fry something?[/QUOTE]
No.
My fm radio kit doesnt make a peep and only at full power the voltmeter moves a tiny bit. Too lazy to trace the error tho.
I was lazy and bought a FM transmitter for like 10 bucks off DX.com :v:
[editline]24th June 2013[/editline]
Anyways, I need some advice on how to convert a sine wave into a square wave.
BUT there's a catch.
the sine wave source in from one of the phases in a cars alternator.
So the voltage range isn't exactly in logic-level friendly territory.
As far as I've gathered it's possible to whip up a sine to square wave converter with a op-amp as main part, but would it be possible to compensate for the voltage fluctuations [B]AND[/B] also reduce the output level to 5 volt or a itty-bitty bit under it?
Something tells me it would also be a good idea to incorporate a opto-coupler on the output stage in order to keep the MCU safe.
Use a voltage divider to bring the input down to a more usable level then feed it into an opto-coupler, on the isolated side use a simple op-amp peak detector, it should be accurate enough for most applications.
[QUOTE=Chryseus;41169922]Use a voltage divider to bring the input down to a more usable level then feed it into an opto-coupler, on the isolated side use a simple op-amp peak detector, it should be accurate enough for most applications.[/QUOTE]
That's the problem, the voltage range fluctuates quite a bit.
Can in short periods go as low as 6 volts, and up to 20v.
A good ol' resistor voltage divider is shit in this case.
[QUOTE=Van-man;41171049]That's the problem, the voltage range fluctuates quite a bit.
Can in short periods go as low as 6 volts, and up to 20v.
A good ol' resistor voltage divider is shit in this case.[/QUOTE]
That's daft, nevermind
[QUOTE=metallics;41171530]Voltage regulator? Might struggle to find something that'll give 5v from 6v supply though[/QUOTE]
it's only for short periods it goes that far up/down, but it's something that [B]MUST[/B] be accounted for or else magic smoke will escape.
Generally it's in the 11v (running with a dead alternator & drained battery) to close to 15 volt (a little bit too "happy" alternator).
[QUOTE=chipset;41162851]After spending weeks slowly moving into this new room I finally got my desk in a reasonably finished and presentable state;
[img]http://puu.sh/3mZaJ.jpg[/img]
The reason for the height difference of the benches is because when doing electronics stuff I tend to want what I'm working on closer to my face so I don't have to bend my back. Though if ever I change my mind I can just shorten the legs.
I've yet to put up all the shelves and that monitor on the floor in the bottom left will fill the gap on the pc bench once I get another wall mounting arm. Plus I've got a couple of HP bench meters and a beefy switchmode lab supply that I need to repair that will join the rest of the EE gear.[/QUOTE]
Is that a MOT i see on the shelf? be careful of that!
[editline]25th June 2013[/editline]
[QUOTE=ddrl46;41156327]Here is a quick and easy way to get them running:
[img]http://forums.parallax.com/attachment.php?attachmentid=67697&d=1266079979[/img]
[url]http://forums.parallax.com/showthread.php/119874-Hard-Drive-Stepper-Motor-with-high-speed-spin-up-circuit?p=88128%C2%AD5#post88128%C2%AD5[/url]
It's not the best way to drive them however since you have to spin it up manually.[/QUOTE]
A better way is to use a 3 Phase IC like the [url=http://www.freescale.com/files/analog/doc/data_sheet/MC33395.pdf]MC33395 Chip[/url]
[QUOTE=Van-man;41171554]it's only for short periods it goes that far up/down, but it's something that [B]MUST[/B] be accounted for or else magic smoke will escape.
Generally it's in the 11v (running with a dead alternator & drained battery) to close to 15 volt (a little bit too "happy" alternator).[/QUOTE]
Are you interested in the voltage or frequency ?
If it's the frequency then any voltage variation does not really matter, just bias the opto-coupler input around 5mA so variation in voltage only results in a small change in current, I.E 11V into 2.2k will give you 5mA, 15V into 2.2k will give you 6.8mA well within tolerance of your average opto-coupler, take the output and use a simple comparator to generate a square wave, isolation isn't even critical for you application as most comparators can tolerate at least 18V on the inputs, just center the reference level at the center of the alternator waveform, this can be done easy enough.
What I would personally do is this:
Attenuate input by 10x
AC couple and add a vcc/2 offset
Use comparator with a vcc/2 reference voltage
This will give a square output with a 50% duty cycle within the limits of the comparators output swing.
If you need a more in depth explanation hit me up on steam later today, or I could draw you a schematic.
[QUOTE=nuttyboffin;41171616]Is that a MOT i see on the shelf? be careful of that!
[editline]25th June 2013[/editline]
A better way is to use a 3 Phase IC like the [url=http://www.freescale.com/files/analog/doc/data_sheet/MC33395.pdf]MC33395 Chip[/url][/QUOTE]
Of course a dedicated IC is a better way to drive it but that circuit will get it up and running for almost free since everyone should have some opamps, resistors, caps and mosfets.
Raided the landfill for goods again.
Found an Epson serial thermal receipt printer, 17" LCD panel with a USB touchscreen interface, a Yamaha EF1000 generator in serious need of repair and oh, a 15000v oil burner starter coil.
[img]http://www.bestbuyheatingandairconditioning.com/Merchant2/graphics/00000001/Transformer%20Oil.jpg[/img]
[QUOTE=Chryseus;41173140]Are you interested in the voltage or frequency ?
If it's the frequency then any voltage variation does not really matter, just bias the opto-coupler input around 5mA so variation in voltage only results in a small change in current, I.E 11V into 2.2k will give you 5mA, 15V into 2.2k will give you 6.8mA well within tolerance of your average opto-coupler, take the output and use a simple comparator to generate a square wave, isolation isn't even critical for you application as most comparators can tolerate at least 18V on the inputs, just center the reference level at the center of the alternator waveform, this can be done easy enough.
What I would personally do is this:
Attenuate input by 10x
AC couple and add a vcc/2 offset
Use comparator with a vcc/2 reference voltage
This will give a square output with a 50% duty cycle within the limits of the comparators output swing.
If you need a more in depth explanation hit me up on steam later today, or I could draw you a schematic.[/QUOTE]
It's only the frequency that matters, but I'd like the output to be within a range any 5 volt powered Micro-controller can handle.
Now that I think about it, most micro-controllers digital-in lines have a tolerance field for whenever they "consider" a signal to be high/low/floating.
[QUOTE=Van-man;41186076]It's only the frequency that matters, but I'd like the output to be within a range any 5 volt powered Micro-controller can handle.
Now that I think about it, most micro-controllers digital-in lines have a tolerance field for whenever they "consider" a signal to be high/low/floating.[/QUOTE]
Here you go.
[img]http://u.cubeupload.com/Chryseus/1lP6oY.png[/img]
Use a LM311 or similar comparator, 4N33 or 4N35 would be a good choice for the opto-coupler.
[b]Edit[/b]
Make R3 and R4 47k
[QUOTE=Chryseus;41186671]Here you go.
[img]http://u.cubeupload.com/Chryseus/1lP6oY.png[/img]
Use a LM311 or similar comparator, 4N33 or 4N35 would be a good choice for the opto-coupler.
[b]Edit[/b]
Make R3 and R4 47k[/QUOTE]
Just out of curiosity, would you change the biasing on the OpAmp to keep the Square Wave Output at a steady 50% Duty? In order to compensate for the transistor? I simulated changing the capacitance in order to change reactance/rc time however that only marginally changed the duty.
[QUOTE=LoneWolf_Recon;41188651]Just out of curiosity, would you change the biasing on the OpAmp to keep the Square Wave Output at a steady 50% Duty? In order to compensate for the transistor? I simulated changing the capacitance in order to change reactance/rc time however that only marginally changed the duty.[/QUOTE]
The capacitor is just there to remove any DC offset.
The output of the opto-coupler is coupled through C1 then offset by 2.5V to ensure it is centered at the reference level of 2.5V, this gives a roughly 50% duty, if you want to vary the duty just change the reference voltage.
[QUOTE=Chryseus;41186671]Here you go.
[img]http://u.cubeupload.com/Chryseus/1lP6oY.png[/img]
Use a LM311 or similar comparator, 4N33 or 4N35 would be a good choice for the opto-coupler.
[b]Edit[/b]
Make R3 and R4 47k[/QUOTE]
I happen to have some [URL="http://www.taydaelectronics.com/lm393n-lm393-ic-low-power-dual-voltage-comparators.html"]LM393N comparators[/URL] and [URL="http://www.taydaelectronics.com/4n28-4n28m-optocouplers-phototransistor-ic.html"]4N28M optocouplers[/URL] laying around.
Probably need to change some resistor values, but they should be able to do the trick.
[QUOTE=Van-man;41197125]I happen to have some [URL="http://www.taydaelectronics.com/lm393n-lm393-ic-low-power-dual-voltage-comparators.html"]LM393N comparators[/URL] and [URL="http://www.taydaelectronics.com/4n28-4n28m-optocouplers-phototransistor-ic.html"]4N28M optocouplers[/URL] laying around.
Probably need to change some resistor values, but they should be able to do the trick.[/QUOTE]
Sounds good to me, the only thing you may need to tweak is R1.
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