[QUOTE=alexaz;39980387]I forgot to mention that the mosfet I've got is logic level. Also Is it common for comparators to break? I guess I could add a check in the MCU for too high of a voltage and cut off the supply incase something goes wrong. That way it would be only a thousand of a second that the device would be exposed to higher voltage than expected. For the gate discharge, would a 10k resistor across gate and ground do the job?[/QUOTE]
Logic level may still not be low enough to ensure saturation but I'd expect some output at least.
Try the gate resistor and if that does not help post the feedback voltage and the transistor you using.
[QUOTE=chipset;39980577]Classic case of getting entrenched in your own idea.
It's when you have a seemingly innovative or different idea that you think is brilliant and pursue that idea without any practical considerations, like if there's actually any demand for the product.
I kinda feel sorry for the guy, he's putting all this hard work and effort into a stupid idea and he doesn't even realize it.[/QUOTE]
I rewrote 5 different statements with regards to this project. On the surface it seemed like a reasonable idea... but the more I thought about it the more I realised it was actually a pretty rubbish idea. I wonder if he will actually hit his funding goal.
I'v added a 10 k resistor across gate and ground, however the shit is till broken.
The R1 in my schematic is a 20 ohm resistor, R2 is 470.
Scenario 1:
The comparators pin voltages:
Positive input: 1.78 V
Negative input (FET source): 1.42 V
Collector output (FET gate): Near VCC
Scenario 2:
The comparators pin voltages:
Positive input: 0V
Negative input (FET source): 0.4 V
Collector output (FET gate): 2.4 V
The mosfets datasheet: [url]http://www.nxp.com/documents/data_sheet/PSMN017-30PL.pdf[/url]
EDIT: Also, it seems like the comparators output doesn't go to ground when the output is supposed to be zero.
[QUOTE=alexaz;39982233]I'v added a 10 k resistor across gate and ground, however the shit is till broken.
The R1 in my schematic is a 20 ohm resistor, R2 is 470.
Scenario 1:
The comparators pin voltages:
Positive input: 1.78 V
Negative input (FET source): 1.42 V
Collector output (FET gate): Near VCC
Scenario 2:
The comparators pin voltages:
Positive input: 0V
Negative input (FET source): 0.4 V
Collector output (FET gate): 2.4 V
The mosfets datasheet: [url]http://www.nxp.com/documents/data_sheet/PSMN017-30PL.pdf[/url]
EDIT: Also, it seems like the comparators output doesn't go to ground when the output is supposed to be zero.[/QUOTE]
After a good deal of thinking I came up with a simple solution that should work (really why didn't I think of this before) just flip the inputs around, so + feedback and - set voltage.
This will correct the problem with the output being inverted.
It probably will not go quite to ground or V+ but there is little you can do about that.
Nothing works. God one day i'll fucking blowtorch this thing down to a brick of plastic.
If that did not work either you've built it wrong or that mosfet is no good, also try increase R1 to 220.
But I would really go with a bjt and an op-amp.
[QUOTE=DrLuckyLuke;39979841]And now for the shitty kickstarter of the month: [url]http://www.kickstarter.com/projects/1531311296/picsu-the-power-supply-that-fits-in-your-computer[/url]
Fucking hilarious[/QUOTE]
Joke's on him, I've just been using an old ATX PSU for my bench-top.
[QUOTE=Zero-Point;39985888]Joke's on him, I've just been using an old ATX PSU for my bench-top.[/QUOTE]
Yea also, who needs five fucking thousand dollars to make that.
[QUOTE=Chezburger;39988770]Yea also, who needs five fucking thousand dollars to make that.[/QUOTE]
Some people use Kickstarter to sell their product instead of using the money to develop their product, I remember there being a seven segment shield (no idea why you'd do a kickstarter for that) on Kickstarter a while ago which showed pictures in which you could see they clearly already have the product but just need to sell it.
Alright, i did even more fucking around and found that the FET doesn't fully turn on even when the comparators output is 3.5 volts, however if i feed 3.5 volts directly from the supply into the gate it does. Might there be not enough current to switch on the mosfet? Yeah, i believe that 3.5 volts is not enough to saturate this FET.
So I'm probably gonna need some beefy TO-220 logic level & protected power Mosfets that can be controlled pretty much directly with common 5V microcontrollers.
Both N channel and P channel would be smashing, and I would be prefer that they can safely handle switching a load at 48 volts safely.
Datasheets for them still give me the dumbs, and I wouldn't be surprised if some of you can name them in your sleep.
The usual cheap places like Tayda or eBay stores with good reputation would be preferable.
[QUOTE=Van-man;39989272]So I'm probably gonna need some beefy TO-220 logic level & protected power Mosfets that can be controlled pretty much directly with common 5V microcontrollers.
Both N channel and P channel would be smashing, and I would be prefer that they can safely handle switching a load at 48 volts safely.
Datasheets for them still give me the dumbs, and I wouldn't be surprised if some of you can name them in your sleep.
The usual cheap places like Tayda or eBay stores with good reputation would be preferable.[/QUOTE]
They may not be cheap, but I pulled some [URL="http://pdf1.alldatasheet.com/datasheet-pdf/view/256224/STMICROELECTRONICS/P80NF55-08.html"]P80NF55-08[/URL] Power N-Channel MOSFETS from an old UPS, and they are pretty hardy/rugged and are still actively produced.
[URL="http://www.st.com/web/catalog/sense_power/FM100/CL824/SC1165/PF64799?s_searchtype=partnumber"]ST Microelectronics - STP80NF55-08[/URL]
[URL="http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313&_nkw=p80nf55&_sacat=0&_from=R40"]Ebay - P80NF55-08[/URL]
[URL="http://www.taydaelectronics.com/catalogsearch/result/?q=P80NF55"]Tayda - P80NF55-08[/URL]
[QUOTE=Chezburger;39988770]Yea also, who needs five fucking thousand dollars to make that.[/QUOTE]
It's no that unreasonable. Buying components for 10 boards costs a lot more than for 100 boards. The more you build, the cheaper it gets. He also gets them manufactured in a pick and place house, so 20$ of each unit probably go towards that.
The setup costs usually are quite high, and they only accept reels of components, so he also has to get them re-reeled at digikey, which costs something like 8$ per reel. Each component becomes its own reel, so you can calculate yourself how much that costs.
The only problem here ist that he went for pick and place assembly instead of manual assembly.
Those fucking transistors... I bought some TIP127's, which are PNP darlingtons that i thought would work with the idea i have. As far as i understand to saturate the transistor current must flow out of base. I have placed a 100 ohm resistor across the base and ground, so the current flowing out of the gate is 35 mA. The problem is that its not fully saturated or something, because while the emitter voltage is 3.5 volts, collector voltage is around 2 (shouldn't it be 3.5 volts since the transistors are supposed to be saturated?). Can someone explain please?
[QUOTE=alexaz;39990165]Those fucking transistors... I bought some TIP127's, which are PNP darlingtons that i thought would work with the idea i have. As far as i understand to saturate the transistor current must flow out of base. I have placed a 100 ohm resistor across the base and ground, so the current flowing out of the gate is 35 mA. The problem is that its not fully saturated or something, because while the emitter voltage is 3.5 volts, collector voltage is around 2 (shouldn't it be 3.5 volts since the transistors are supposed to be saturated?). Can someone explain please?[/QUOTE]
What collector load are you using, is there any resistor on the emitter, draw your circuit.
There should be close to 3.5V on the collector.
[img]http://i.imgur.com/FvLMHYx.png[/img]
Sorry for the crudeness of this schematic.
R3 and R4 are 100 ohms.
Collector voltage is only 2.9V
-duh nevermind-
Ahh of course your losing ~0.8V across the first transistor so the second one sees 2.9V rather than 3.5V on the emitter.
Your not going to be able to get the output right to the supply voltage, you could use a single PNP but then you have significant base current (depending on the max current it may be ok).
Let me make one point perfectly clear, your not going to get 3.5V or whatever your supply voltage is out, all linear regulators have a voltage drop.
Use a normal BJT, not a darlington transistor.
Hey guys, I know someone here poked me to post my 3d printing in thsi thread previously, so here's waht I've been working on over the past few days.
I have been designing some small mounting plates for my university group project this morning:
[t]https://dl.dropbox.com/u/3798635/sketchup1.png[/t]
[t]https://dl.dropbox.com/u/3798635/sketchup2.png[/t]
The idea is these will mount an existing rc helicopter body onto a flat metal plate. I'll post pictures once it is done, but these were a royal pain to design since I tried to stick to the following constraints
a) Using existing mounting holes on the plate and heli chasis only
b) minimal size/volume/weight
c) not alter the downward airflow from the rotors above
and the most difficult
d) design it in such a way you can actually bolt the damn things together in such an order that it is actually assemblable.
[editline]20th March 2013[/editline]
Just printed in PLA and remembered this:
[QUOTE=HiddenMyst;39524568]So I hear PLA smells quite pleasant while printing. Is this true?[/QUOTE]
Got as close up to the thing while it was printing as I dared and I can confirm it does smell pleasant. Over the standard garage oil and timber stench its hide to make out exactly what it smells of bu t I'd liken it to freshly cut celery.
[t]https://dl.dropbox.com/u/3798635/2013-03-21%2016.50.38.jpg[/t]
[t]https://dl.dropbox.com/u/3798635/2013-03-08%2011.45.22.jpg[/t]
Top: My printed mounting points on top of the plate they join to.
Bottom: a side view of the metal plate with the rest of the structure below it including one of my Arduino mount/bumpers I also printed.
Hopefully within the next few days I'll have a photo of it all bolted together.
Reminds me, currently tinkering with designing a 3D printer controller board that fits my needs.
So that means Toshiba THB6064AH Stepper motor drivers (for driving the steppers, D'uh) and a ATMega AT90USB1286 for controlling it.
I'd probably have to buy a Teensy++ and a handful of the Toshiba chips to dick around with before actually making a PCB.
[QUOTE=Van-man;39999048]Reminds me, currently tinkering with designing a 3D printer controller board that fits my needs.
So that means Toshiba THB6064AH Stepper motor drivers (for driving the steppers, D'uh) and a ATMega AT90USB1286 for controlling it.
I'd probably have to buy a Teensy++ and a handful of the Toshiba chips to dick around with before actually making a PCB.[/QUOTE]
Don't get it the wrong way, but [url]http://sivers.org/zipit[/url]
I can confirm this is correct in 95% of all cases
[QUOTE=DrLuckyLuke;40001080]Don't get it the wrong way, but [url]http://sivers.org/zipit[/url]
I can confirm this is correct in 95% of all cases[/QUOTE]
I'm already prepping a orderlist and basic schematics, I just need some wiggle room in my budget to buy the parts.
Literally the only thing holding me back is money.
[QUOTE=Van-man;40001179]Literally the only thing holding me back is money.[/QUOTE]
It always is.
I've recently discovered the greatest thing since sliced bread for us on a tight budget; Accepting projects for others where materials are paid but your labor is free.
So far in the past month or two I've gotten to vastly expand my carpentry skills in a way that I would otherwise not have been able to because I agreed to build my sister some tables for her LARP-ing. She payed the nearly €100 in materials (as well as lending me money to buy a miter saw) and all I had to do was put it together. I've learned more about carpentry and working with wood in the past week than in my entire life previously or that I would have for years to come.
On that same note, I agreed to install some decorative lighting for my other sister in the form of RGB LED strip lighting. All in all it's gonna be nearly €50 in materials which she pays and I get invaluable experience in making permanent installations and I get to dick around with stuff that I couldn't justify buying myself on my budget.
Offer your services as often and as loudly as you can and you will never want for projects while still keeping a full wallet. Just remember to follow through with your promises and always be realistic and self critical. If you don't think you can do it, be honest about it or you may end up with a bigger bite than you can chew. And debt. And ruined relations.
Am I correct if I assume the Inverting Schmitt trigger in this picture is used for isolating the signals from the optical encoder?
[t]http://s20.postimage.org/y5izqkj71/encoder_board_schematic.jpg[/t]
[QUOTE=chipset;40001553]It always is.
I've recently discovered the greatest thing since sliced bread for us on a tight budget; Accepting projects for others where materials are paid but your labor is free.
So far in the past month or two I've gotten to vastly expand my carpentry skills in a way that I would otherwise not have been able to because I agreed to build my sister some tables for her LARP-ing. She payed the nearly €100 in materials (as well as lending me money to buy a miter saw) and all I had to do was put it together. I've learned more about carpentry and working with wood in the past week than in my entire life previously or that I would have for years to come.
On that same note, I agreed to install some decorative lighting for my other sister in the form of RGB LED strip lighting. All in all it's gonna be nearly €50 in materials which she pays and I get invaluable experience in making permanent installations and I get to dick around with stuff that I couldn't justify buying myself on my budget.
Offer your services as often and as loudly as you can and you will never want for projects while still keeping a full wallet. Just remember to follow through with your promises and always be realistic and self critical. If you don't think you can do it, be honest about it or you may end up with a bigger bite than you can chew. And debt. And ruined relations.[/QUOTE]
Already do that.
Even did complete LED illumination here & there using warm white LED strips.
For the smaller sections, a fan controller meant originally for computers work excellent as a dimmer for 12volt strips
I even scrounge old electronic equipment for components & parts.
Recently gutted 3 printers and 1 scanner, all those stepper motors & cogwheels :quagmire:
[t]http://i.imgur.com/fxLe1cL.png[/t]
Was rather bored so I designed a 300W constant current / constant power load for testing power supplies, it can handle a maximum of 30A at 10V which is more than enough to test all but the highest power supplies.
It uses two parallel 2N3055 to handle the power and has outputs that can be fed into an ADC for monitoring voltage and current, the current can be set either by a DAC or even a pot.
Now just to get myself some parts to build it.
So I bought 1.5m of solder wick from ebay.
[T]http://i.imgur.com/bogJNGo.jpg[/T]
I don't think I'll have problems with exposing smaller photosensitive PCB's ever again.
[T]http://filesmelt.com/dl/DSC000025.JPG[/T][T]http://filesmelt.com/dl/DSC000039.JPG[/T][T]http://filesmelt.com/dl/DSC000045.JPG[/T][T]http://filesmelt.com/dl/DSC000056.JPG[/T][T]http://filesmelt.com/dl/DSC000065.JPG[/T][T]http://filesmelt.com/dl/DSC000085.JPG[/T]
3 UV LED's each consuming 3 watts, bolted onto a old Pentium 3 era heatsink.
[QUOTE=Van-man;40011659]I don't think I'll have problems with exposing smaller photosensitive PCB's ever again.[/QUOTE]
You should have used some UV tubes, they give a much more even exposure, as it is areas close to the LEDs are going to be overexposed.
Or use a diffusor (thin paper)
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