Hooray, got my 320 * 240 LCDs to do something!
[t]http://i.imgur.com/XnP08mC.jpg[/t]
I'v been fucking trying to figure this out myself but i'm out of ideas.
[img]http://i.imgur.com/VeaELyM.png[/img]
The darlington pair is controlled by the microcontroller with a PWM signal, thefore the voltage across the load can be anything from 0 to 12 volts, however now with the darlington i have completely lost the feature of sensing current since it looks like the ADC input pin is always floating ( or just when the transistor closes due to PWM). I'v tried putting a 10k resistor to ground inbetween the load and shunt resistors but that doesn't seem to fix anything. Also, how would i go and measure the voltage across the load?
God i fucking hate transistors.
[QUOTE=alexaz;39857623]I'v been fucking trying to figure this out myself but i'm out of ideas.
[IMG]http://i.imgur.com/VeaELyM.png[/IMG]
The darlington pair is controlled by the microcontroller with a PWM signal, thefore the voltage across the load can be anything from 0 to 12 volts, however now with the darlington i have completely lost the feature of sensing current since it looks like the ADC input pin is always floating ( or just when the transistor closes due to PWM). I'v tried putting a 10k resistor to ground inbetween the load and shunt resistors but that doesn't seem to fix anything. Also, how would i go and measure the voltage across the load?
God i fucking hate transistors.[/QUOTE]
With PWM being feed into that darlington, you'll be getting spurious signals on the ADC channel.
[QUOTE=alexaz;39857623]I'v been fucking trying to figure this out myself but i'm out of ideas.
[img]http://i.imgur.com/VeaELyM.png[/img]
The darlington pair is controlled by the microcontroller with a PWM signal, thefore the voltage across the load can be anything from 0 to 12 volts, however now with the darlington i have completely lost the feature of sensing current since it looks like the ADC input pin is always floating ( or just when the transistor closes due to PWM). I'v tried putting a 10k resistor to ground inbetween the load and shunt resistors but that doesn't seem to fix anything. Also, how would i go and measure the voltage across the load?
God i fucking hate transistors.[/QUOTE]
Try and measure it with a scope.
[QUOTE=LoneWolf_Recon;39857923]With PWM being feed into that darlington, you'll be getting spurious signals on the ADC channel.[/QUOTE]
That's what i'm getting
[QUOTE=DrLuckyLuke;39858146]Try and measure it with a scope.[/QUOTE]
Haven't got one yet.
You could attempt a sample and hold setup if you want to measure the voltage:
[URL="http://www.falstad.com/circuit/e-samplenhold.html"]http://www.falstad.com/circuit/e-samplenhold.html[/URL]
[QUOTE=alexaz;39857623]God i fucking hate transistors.[/QUOTE]
Try this:
[img]http://puu.sh/2eWA4[/img]
The sense voltage is of course V = I * Rsense
oh god, i'm running my first computer lab for Introductory Digital Systems at my uni tomorrow
i'm so unprepared, the lecturer has given me 0 training and everything is so disorganised - i don't even have a staff id
[editline]10th March 2013[/editline]
I think I'll just run them through the basics, converting hexadecimal to be displayed on a seven-segment display. it's what my tutor did last semester when I was doing the course
Linear slide potentiometers.
Where can I get one that's over 10cm for cheap?
RS components have some, but they're expensive (excluding delivery)
[url]http://www.ebay.co.uk/itm/Slide-Potentiometer-Linear-500K-Mixer-Variable-Resistor-/290871852117?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43b9503c55[/url]
Those things are fucking expensive. I bet it would be cheaper to have a capacitive slider than a mechanical one.
[QUOTE=alexaz;39874548][url]http://www.ebay.co.uk/itm/Slide-Potentiometer-Linear-500K-Mixer-Variable-Resistor-/290871852117?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43b9503c55[/url]
Those things are fucking expensive. I bet it would be cheaper to have a capacitive slider than a mechanical one.[/QUOTE]
That's actually quite cheap.
OK kids, it's time for [I]""Mystery IC of the day""
[/I]Bet none of you can find a datasheet on this bugger, since I couldn't
[IMG]http://filesmelt.com/dl/mystery_ic.png[/IMG]
[SUP]The Comic Sans text is the physical description of it.[/SUP]
[QUOTE=alexaz;39874548][URL]http://www.ebay.co.uk/itm/Slide-Potentiometer-Linear-500K-Mixer-Variable-Resistor-/290871852117?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43b9503c55[/URL]
Those things are fucking expensive. I bet it would be cheaper to have a capacitive slider than a mechanical one.[/QUOTE]
Trust me, that's MUCH cheaper than Farnell or RS Components.
Cheers for the help.
-snip-
Does the load on the n channel mosfet must be connected to the drain only, or can it be connected to the source too?
[QUOTE=alexaz;39876466]Does the load on the n channel mosfet must be connected to the drain only, or can it be connected to the source too?[/QUOTE]
If your talking about a similar circuit to what I posted above the load should be on the source, keep in mind for optimal performance you need a MOSFET with low RDS (drain-source resistance) although they still can't really compete with BJT's in that respect so a BJT is preferred.
I ordered some logic level mosfets with Rds(on) of around 30 milliohms. I went with them because i believe it would be cheaper and for some reason i'v always hated BJT's because whatever i build with them - none of that shit works.
I'm considering making a small spotwelder using a beefy transformer. I was wondering if I could connect the primary straight to the mains, or would I need a power supply?
[QUOTE=chaz13;39889277]I'm considering making a small spotwelder using a beefy transformer. I was wondering if I could connect the primary straight to the mains, or would I need a power supply?[/QUOTE]
I'd put a breaker inbetween the mains and transformer, so that you don't fuck shit up too bad if you do fuck shit up (otherwise you'll be fine).
Who would've thought that the AVR's protection diodes to VCC actually make all pins sink current when VCC = 0V.
[QUOTE=chaz13;39889277]I'm considering making a small spotwelder using a beefy transformer. I was wondering if I could connect the primary straight to the mains, or would I need a power supply?[/QUOTE]
Use a microwave transformer, rather a pain in the but without the proper tools but its definitely worthwhile for a first time spot welder.
[URL]http://hackaday.com/2009/06/23/how-to-build-your-own-spot-welder/[/URL]
EDIT:
Yeah it looks like directly into the mains on the secondary
[QUOTE=LoneWolf_Recon;39892980]Use a microwave transformer, rather a pain in the but without the proper tools but its definitely worthwhile for a first time spot welder.
[URL="http://hackaday.com/2009/06/23/how-to-build-your-own-spot-welder/"]http://hackaday.com/2009/06/23/how-to-build-your-own-spot-welder/[/URL][/QUOTE]
That was my plan! :smile:
My first greenwire fix:
[thumb]http://i.imgur.com/2nMCxBa.jpg[/thumb]
[thumb]http://i.imgur.com/YiHs0CL.jpg[/thumb]
[editline]13th March 2013[/editline]
My only regret is that I didn't actually have any green wires
[QUOTE=DrLuckyLuke;39901189]My first greenwire fix:
[thumb]http://i.imgur.com/2nMCxBa.jpg[/thumb]
[thumb]http://i.imgur.com/YiHs0CL.jpg[/thumb]
[editline]13th March 2013[/editline]
My only regret is that I didn't actually have any green wires[/QUOTE]
I prefer yellow wires instead.
I like to be reminded of my mistakes, so I don't repeat them.
[QUOTE=Van-man;39902603]I prefer yellow wires instead.
I like to be reminded of my mistakes, so I don't repeat them.[/QUOTE]
Well, the mistake I made was pretty tough to anticipate if you didn't know about it :v:
[t]http://i.imgur.com/njo9q3Z.jpg[/t]
My parts arrived!
[QUOTE=Van-man;39902603]I prefer yellow wires instead.
I like to be reminded of my mistakes, so I don't repeat them.[/QUOTE]
I bought six feet of telco trunk cable. Makes your job much more colorful.
[QUOTE=Lapsus;39907682][t]http://i.imgur.com/njo9q3Z.jpg[/t]
My parts arrived![/QUOTE]
Hobbyking? I have that same balancer, and charger.
[QUOTE=Lapsus;39907682][t]http://i.imgur.com/njo9q3Z.jpg[/t]
My parts arrived![/QUOTE]
god dr pepper so much want
Really.
[QUOTE=DrLuckyLuke;39903338]Well, the mistake I made was pretty tough to anticipate if you didn't know about it :v:[/QUOTE]
Tell us more!
[QUOTE=metallics;39909144]Tell us more![/QUOTE]
[QUOTE=DrLuckyLuke;39889871]Who would've thought that the AVR's protection diodes to VCC actually make all pins sink current when VCC = 0V.[/QUOTE]
That basically pulled down the SET-input of my NAND flipflop, even though I didn't want it to.
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