Another SMD lebowski PCB

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.
 
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.
 
stepper motor scr for reflow oven web2.png

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.
 
Some actual progress this evening.

graph of 2nd reflow temp.png

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

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
and it is repeatable, YUS!
 
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.
[youtube]_sgqLkquU6c[/youtube]

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.
[youtube]jLmnNlb4q7k[/youtube]

a couple of fairly dry youtube clips to update you all.
 
So I tested the PID control of the reflow oven tonight. This was very frustrating, I think I've rectified a few bugs in my code and understand the stepper motor a little more now. One frustration is that if I use 100% speed on the stepper, the quick ramping up of the power in the AC knocks out my serial connection to the pc so I can collect the data but I know the Arduino is still chugging away as the stepper is still adjusting to get the heat curve right.

So another annoyance is that my oven is starting to misbehave in that it is stalling at about 100degrees C before carrying on with the heating and sometime its losing power even though the SCR isn't turned down. Not sure why this is, I think it might have an internal temp sensor in it that is a thermal shut off that is misbehaving. I may have to find out and hard wire in a fix resistance to ensure max power.

I am also thinking that the fan is maybe not really helping at all. I might be best disconnecting the fan leads, removing the metal protector and using a shallower glass bowl that has less volume thus can heat up quicker. In the first part of all my graphs the oven is playing catch up to the curve. Doing this should get the heating element closer to the PCB

anyway The PID is working really well now and I am also thinking of testing it with an clothes Iron like Lebowski has suggested a while back. The beauty of this setup is that I can pretty much plug any heat source into it.

Makes me think about PID for cooling hub motors, that's quite a good application for it really.

https://docs.google.com/spreadsheets/d/1UM1lZf8ooyoxMYedPQHIJL8rDLM4hVoxKliKL3TLeQU/edit?usp=sharing

if people are interested here is my current trial runs using the PID logic.
 
Had a go this weekend applying solder paste using the almost correct stencil. I've come the realisation that for 10 of these I want to do it right every time with as little rework as possible so I have ordered yet another stencil. This is the 3rd one now so any profit is draining from this project rapidly.

also took and inventory of the parts I have and what I still need. I was missing a max809 chip and a 1206 4r7 resistor so have ordered them from ebay as well as the correct stencil for the wson chip from oshstencils.

I should have the initial prototype for testing by bas and emgee this weekend and then I guess bas will have to flash me the other nine smt pic chips pending the first being a success.

In my inventory I also discovered I am short of the smallest resistors for the initial batch of 10 boards again I will hit up ebay for the specific values as in the UK the min order at any of the big electronics resellers is always crippling.

Thanks every one for their patience, mine specifically is wearing thin.

also my halogen fan ovens motor has died but this is okay for 4 minute runs, the lid gets very hot and ive disconnected the temp sensor in side the oven so that its only controller externally by the scr Arduino and thermocouple feedback loop.

I tried the Arduino with the clothes iron I have and it does get hot quickly and I worry that it will damage the components if I go that route.
 
max809 chip arrived, just waiting on stencil and 4r7 1206 resistor
 
I have now received the 3rd stencil and now printed a design for holding my £4 magnifying glass to the rim of the ikea tertial lamp. This will allow me two hands when placing the tiny resistors under the magnifier.

Should have a crack at making the first of 10 up tonight. Pictures to follow
 
first smd board reflowed. I did everything bar the main chip, big inductor and largest ceramic cap, cause the last two need handsoldering and the main chip scares me since i've only got one to play with. I want to test the dcdc power supplies before i solder in the chip and accidently smoke it somehow.

Anyway it went pretty well, my halogen oven broke before i even got chance to use it so i took apart the delta toaster oven i bought initially for the task for £6 and took the temp cut off out of circuit. I monitored the temps via the com on the arduino but they never seemed to get anywhere near as hot as the ideal heat curve. It looks nicely reflowed though. Will take it to work and get some photos up tomorrow.

My magnifier was perfect though. I spent all of £3.99 on it but the mount i made for my ikea lamp transforms it into a very handy piece of kit for the production of tiny things.

Anyway its 1:36 am now and i started this at about 8.30pm so i feel like ive done a days work already. Will be quicker next time. i need to get a system regarding the inventory when i'm doing the batches. Also my stencil holder needs to be flatter to get a nicer cleaner layer but i am still learning.

Pleased though since this prototype can pretty much go to lebowski for him to test the rest on his matching powerboard.
 
Nice one, looking forward to pics.

I use a Stereo microscope for soldering, but all work is done by hand even down to 0603 components. The TQFP44 chip is not hard to solder by hand, use lots of flux, and a solder blob that is about 3 pins wide, then just run the iron from one side to the other, by the time you're at the end, all solder will be spent and usually with no bridges.

Good luck.

Andy
 
Some pics for Andy and others
IMG_20180213_211647.jpg
magnifier attachment
IMG_20180213_211654.jpg
magnifier attachment in the light
IMG_20180213_211753.jpg
My solder paste jig plastic printed
IMG_20180213_211816.jpg
my newly reflowed board
IMG_20180213_211829a.jpg
Bobc original handsoldered board
boards sxs.jpg
the two boards side by side.

Also a propos of nothing (I sent a thank you email, that's it) Digikey sent me a pcb ruler which doubles as a gauge and table for lots of wires, machine screws, smd packages. A really swish double sided piece of kit, better than all my received Christmas presents this year. I sent the thank you email as they managed to fulfil my order and ship it from America to the UK in under 48 hrs. Absolutely astounding service and shipping. Go them. I am in no way affiliated with the company aside from being a customer.
 
IMG_20180309_004138_480x727.jpg
So this is the latest smd offering. Still have to hand solder the 220uH inductor and a capacitor and maybe some high value resistors to trim the voltages but aside from that I am quite happy with my second attempt. Learning all the time. Still hand placing with tweezers and magnifying glass. Took above 3hrs. Wife got bored so came downstairs to see what I was doing. I now have a very organised electronics lebowski project box. She was quite interested by the end. I am a lucky man. Not sure she is a lucky woman.
 
right, I feel now we are getting close to building batches for customers I should put out my prices. Ive tried to be fair and I hope that people wont be disappointed.

£75 which comes from

£5 per board
£16 in parts (this included things like my magnifying glass @£4 and toaster oven @£6) plus all the other parts / 10
£19 main chip
£30 labour/time (probably a huge underestimate)
£5 Postage

When you compare this to fully built latest vesc offerings its actually reasonable (you may argue that this isn't the full controller but I cant really build them for less without making losses) Thanks everyone for the support and following this thread.

Just Pm'd everyone who already specified an interest.
 
Not disappointed at all, if we would have to do it by ourselves we wouldn't save much. For me, the pleasure to follow all your (and bobc's!) efforts is already worth the money. Please mention if you expect a PM right now to order or if you first try to find out a reasonable number of interested people who could announce their interest publicly here.
I'm in for 1 pcs (as a start...).
 
So here is the update,
Spoke to Bas(Lebowski) via PM

Lebowski and Emmgee will test prototype 2 on Emmgee's bike when it gets to Switzerland (posted on Sunday 11/03/2018). There still maybe issues with led polarity or not, remains to be seen but the psu ones (all the greens) and the 3rd one down in the 4 drive leds definitely work. This will be triple checked before I make the next 7.

Using the money from the first two payees to buy the flashed main chips from Lebowski so that is going to immediately be reinvested to get the project speeded up as fast as possible.

he has 7 chips on hand so I will take them all 25chf*7 +5chf postage so £142 (after paypal costs) straight back into the project.

I now have a glamourous assistant in the form of my wife so that will speed up production too. Gives her something to do other than watching Aussie soap operas. I think she got interested when she realised there was money coming back in versus always going out on my projects.

@ElectricGod, thanks for the update i've taken the decision to bump people up the existing list whose money I already have, without this money no body gets a brain board so I think this is fair. Rest assured thought I will have your board(s) made in a timely manner as I will build the rest in batches.

I wont send out any boards before payment though as I have been stung before by the odd customer for the bare larger pcbs (and these have taken a lot more of my time, money and energy).
 
whereswally606 said:
So here is the update,
Spoke to Bas(Lebowski) via PM

Lebowski and Emmgee will test prototype 2 on Emmgee's bike when it gets to Switzerland (posted on Sunday 11/03/2018). There still maybe issues with led polarity or not, remains to be seen but the psu ones (all the greens) and the 3rd one down in the 4 drive leds definitely work. This will be triple checked before I make the next 7.

Using the money from the first two payees to buy the flashed main chips from Lebowski so that is going to immediately be reinvested to get the project speeded up as fast as possible.

he has 7 chips on hand so I will take them all 25chf*7 +5chf postage so £142 (after paypal costs) straight back into the project.

I now have a glamourous assistant in the form of my wife so that will speed up production too. Gives her something to do other than watching Aussie soap operas. I think she got interested when she realised there was money coming back in versus always going out on my projects.

@ElectricGod, thanks for the update i've taken the decision to bump people up the existing list whose money I already have, without this money no body gets a brain board so I think this is fair. Rest assured thought I will have your board(s) made in a timely manner as I will build the rest in batches.

I wont send out any boards before payment though as I have been stung before by the odd customer for the bare larger pcbs (and these have taken a lot more of my time, money and energy).

I wouldn't expect anything different. You have to protect yourself and theirs lots of crooked people out there!
 
Thx EG,

Anyway another package at work today. Not the main chips yet(they are enroute) but another batch dcdc chips. These are the lm5017 soic8 chips which go with the original 200 bobc brain pcbs I ordered. Now I have potential to make more boards as I'm no longer restricted by the dearth of this particular dcdc chip.

I originally ordered 15 of the wson8 variant circuit board so the first 15 will be of that variety. The next 10 will be bobc's original design (soic8 lm5017) type. It shouldn't change anything really the spec of the components is the same.

They were due to come in may, then end of march and now 15/03/2018 so this is pretty early considering they were on back order. I actually thought I cancelled this order so was a surprise to the finances when farnell took the £50 out of my account.

I have also been thinking about a test rig my end. I still have the mti85 power stage, this doesn't have the drivers or current sensors on it.

My thought is that I can save some monies initially by using the newest Lebowski power board as the interface between the bobc brain and the bobc mti85 power stage. That way I can check the brains fully before posting them out. i.e. have a motor running from them and have it hot swappable for each new brain to test. This is my plan as of today. This is also because id like to make use of the mti85 powerboard in my Emax scooter as bob and I initially intended.
 
Received another package from the big "L"

7 main pic chips. And the first prototype back for repairs.

Going to start batch production tomorrow evening testing then to follow. Big thanks to all those who have already paid I hope to have you boards ready soon.
 
@ coleasterling - paid
@ Minimum - paid
IMG_20180318_223120WebSize.jpg
here are three boards I reflowed last night, they have still got to have the 220uH inductor and another cap hand soldered on but they are mostly done. Need testing also but these will go out to coleasterling, Minimum first. Emmgee (betatesting) has prototype 2 (which has the changes these boards have)

To the rest of this list please let me know if you are interested still as I need to know for buying parts etc.
Electric God *2
Sparkiesweden
Snowchyld
Mobilis (smd or through hole)
progrock *2
Beez65 *2
VadimZ *2
 
thanks Cole.

Done another 3 last night (so 6 now), I still have to hand solder on the inductor and the poor fitting cap (which consequently cant be reflowed).

Waiting for prototype 2 tests before releasing them out into the wild. Bas (Lebowski) has this and is testing soon. I also need to build my power stage to personally test them all on a motor before sending them out but not long now. Thanks for all your patience.

One worry I have is the proximity of the 4 drive leds to each other. It is hard to ensure that they don't touch at the non ground side where they shouldn't be common. I may have to invest in a hot air gun to rework this if it proves to be an issue. Definitely an area for improvement on the brain pcb design.
 
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