Another SMD lebowski PCB

Electric Motors and Controllers
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Lebowski
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Re: Another SMD lebowski PCB

Post by Lebowski » Dec 13, 2017 3:04 pm

Try calculating their cost by weight... :shock:

whereswally606
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Re: Another SMD lebowski PCB

Post by whereswally606 » Dec 27, 2017 3:45 pm

So I had ago at putting a digital pot 10k into a Chinese scr. I desoldered the 500k 2w ohm pot and soldered a 3 wire breakout to go to my breadboard. I then wired up the digital pot to the nano and to the scr. It had a looping code which continuously turned the wiper up to 128 and back down to 0.

However when I went to test it on a router, it didn't appear to work and I'm guessing it's because the pot that came out was for 500k and this digital pot is 10k.

I wanted to double check that I'd uploaded the code so I did something stupid which was plug the nano back into my pc before unplugging the mains. Big spark, dead nano and for a moment thought I'd killed my pc. However luckily was just the RCD tripped to cut the mains power to everything.

So plan c is I have a spare 5 wire stepper motor and so I've just bought a uln2003 driver for it to use it on the nano. I will use the stepper to turn the 500k pot mechanically which will allow me to use my pc to monitor the serial of the nano in real time and not have to use the ropey Nokia LCD for output. I know this is a rube Goldberg approach but I think it's the safest for me right now and I know it will work.

Plan d is to build one of Andy browns through hole smd reflow controller boards. But I hope I can avoid that.

Still not received the new PCBs from pcbway as they are delivering to work and I'm not there till the new year. Hopefully January will be more productive.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
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whereswally606
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Re: Another SMD lebowski PCB

Post by whereswally606 » Jan 11, 2018 10:15 am

received the new wson pcbs yesterday. I have sent off today for a new solder paste stencil from oshstencils which cost about £10 but I think worth it to get the accuracy I need deploying the paste layer.

My friend has a stencil cutting machine but I don't think it has the accuracy of pitch so a tenner is really here nor there at this point.

I had some success with building a nano Arduino and stepper driver to turn the pot on the SCR so I almost have a reflow oven operational. I can see this happening soon now. I only have one pic chip from bas ("lebowski") at the moment and the first prototype is off to him to run on his power board when I build it. Customers ones to follow.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

whereswally606
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Re: Another SMD lebowski PCB

Post by whereswally606 » Jan 15, 2018 5:57 am

stepper motor scr for reflow oven web2.png
stepper motor scr for reflow oven web2.png (241.35 KiB) Viewed 90 times
Here is the progress on my automation of the dimmer switch for my reflow oven. I worked out how to control the stepper forward and backward one 3/4 turn so that the dimmer is fully on and fully off with no overshoot. Now i can use this code with my old relay code directly, or modify it slightly so that it varies the dimmer relative to the heat differential of the target temp and the actual temp in the halogen oven. Some familiar to the mpcnc project my recognise my repurposing of the pineapple connector which had been superceeded in the mpcnc design.

still to do.

receive new wson stencil from oshstencils for 15 boards with variant wson chip (should be soon)
modify halogen oven with silver foil and reduce angle off fan blades to reduce their power blowing about the little smd pcb parts.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

whereswally606
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Re: Another SMD lebowski PCB

Post by whereswally606 » Jan 16, 2018 7:09 pm

Some actual progress this evening.
graph of 2nd reflow temp.png
graph of 2nd reflow temp.png (53.01 KiB) Viewed 56 times
So this wavy line is the bang bang fully on fully off algorithm as collected via the serial port.
temp in degrees C on the Y axis, time in seconds on the X axis.

I don't know whether this is really good enough for a decent reflow and i still need to reduce the fan speed/angles to reduce the turbulence in the oven but it represents a huge step forward for me in following the reflow curve.

I should be able now to make a better pid algorithm which can produce a tighter fit to the curve. There is not a way to easily cool the oven after the apex, best at that point to take the lid off the oven. Ignore the heat at the start too, that was the residual heat from several unsuccessful trial runs.
reflow setup with a stepper motor SCR.jpg
reflow setup with a stepper motor SCR.jpg (84.14 KiB) Viewed 56 times
And here is the latest offering. Gonna run one more trial before bed.
And if you have been following, thanks.
graph of 3rd reflow temp.png
graph of 3rd reflow temp.png (12.61 KiB) Viewed 56 times
and it is repeatable, YUS!
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

Animalector
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Re: Another SMD lebowski PCB

Post by Animalector » Jan 16, 2018 7:35 pm

just re-discovered this thread. Nice work

Andy

whereswally606
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Re: Another SMD lebowski PCB

Post by whereswally606 » Jan 17, 2018 7:28 pm

As of this evening i think i may have implemented PID instead of simple bang bang algorithm. Not gonna test it now. It's too late and i made that mistake last night. But the logging in the serial monitor and the turning on the stepper look good so i think it might produce an even nicer heat curve graph. If this is the case it might be worth refining the array which describes the target heat graph. i.e. get my temp target numbers closer to the ideal reflow curve.


In other news i plastic printed a holder to aid my stencil pasting which will keep the pcb from sliding about as i apply the solder paste.

And i also printed an eight of my sprocket for my Tom Stanton style RC bike. 224tooth htd5 pulley.


a couple of fairly dry youtube clips to update you all.
Distributing "Lebowski" FOC Controller PCB (Through hole) since 2016
Moped: Emax 110s 2009

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