Surface-mount cyberbanking apparatus are all-over in production, but abounding hobbyists are still appliance old-style through-hole technology, sometimes exclusively — including me, until recently. Why accept accidental cyberbanking tinkerers shied abroad from surface-mount accessories (SMD) in favor of through-hole (TH)? TH is abundant earlier and accepted for prototyping, but the allowances of SMD are too big to ignore. Although optimized for automatic accumulation e.g. with pick-and-place systems and reflow ovens, abounding do-it-yourselfers accept amorphous to move to SMD, at atomic partially. It does affectation some altered challenges than through-hole, but some things are easier, too.
This is my aboriginal attack into SMD, let’s analysis it out.
No big-ticket accessories is bare for surface-mount, at atomic in low-volume, you can get buy with not abundant added than a soldering iron.
Most important: a surface. Not a solderless breadboard: that is, not bounce terminals as apparent in Cyberbanking activity kits: calmly on with a best 160-in-1, nor the added accepted through-hole breadboards as apparent in Notes on prototyping ambit boards: breadboards, perfboards, and aloft accepted for through-hole prototyping are not workable. Printed ambit boards are capital for surface-mount technology.
If you’re absolutely desperate, you can adhesive surface-mount apparatus after a surface: cast the accessory over, anxiously adhesive on affairs assimilate anniversary lead. Known as asleep bugging, this address is not preferred, except alone as a aftermost resort, archetype from SPI interfacing experiments: EEPROMs, Bus Pirate, ADC/OPT101 with Raspberry Pi:
To accumulate your sanity, use a ambit board, accouterment an absolute apparent for the surface-mount components.
Even 0.1″ through-hole perforated boards can assignment analytic able-bodied for surface-mount. I’ll use a single-sided 5×7 cm cardboard nut lath from:
As for the components, we’ll charge an array of surface-mount resistors and capacitors. SMDs are accessible in a array of sizes, some too baby to calmly accumulate after appropriate accessories (microscope, loupe, or pick-and-place machine).
0603 (imperial) is about the aboriginal about accessible for duke assembly. You can go abate (0402 or below) but you’re activity to accept a bad time aggravating to hand-solder, or beyond (0805 or above) but at greater amount and lath space. 0603 is a acceptable best for general-purpose apparent arise prototyping.
Components are awash in band & reel packaging, in quantities of thousands:
but this is too abundant for my apprehensive purposes. To break this, one can acquirement a sample book, absolute a abate abundance of apparatus of a ample cardinal of values.
The accumulated resistor/capacitor sample books are absolutely convenient, you can put it on shelf for storage, it doesn’t booty up abundant space, and aback you charge a basic you can cast the pages and aces out the able basic component. No charge for basic cabinets or boxes. I bought this one:
and it accustomed in 11 days:
For my aboriginal activity with these components, I absitively to anatomy a surface-mount adaptation of activity #9 “Electronic Woodpecker” as apparent in Cyberbanking activity kits: calmly on with a best 160-in-1. Here it is:
Not 100% surface-mount: acclimated a through-hole resistor to alter the potentiometer (but army on the surface), and additionally a through-hole electrolytic capacitor and PNP transistor (2N4403) aback that’s all I had. The 0603 apparatus are tiny: alike the adhesive bridges are bigger! The aboriginal adaptation of this lath was unsuccessful, the capacitances were too low to aftermath audio oscillations, so I anchored on some through-hole bowl caps in parallel:
while the ambit was live, so the change in capacitance as the basic cooled bottomward could be heard through the apostle output. With the two 104 (= 0.1 µF) capacitors in parallel, the accustomed woodpecker complete aftereffect is back. Again, not a 100% surface-mount board, but a start.
To get added convenance with surface-mount, I angry to:
Purchased this soldering convenance kit: 2016 New Both Abandon SMT SMD Cyberbanking Basic Welding Convenance Lath PCB Soldering DIY Kit Skill Training Mini Version, for 99¢ including chargeless shipping. The kit accustomed in 13 days, with the board, parts, and a manual:
The chiral is not in English, but I can apprehend the advertence designators, basic values, and footprints:
The lath is absolutely complete and the pads appear pre-tinned with solder:
Some advance soldering the board:
The agent may accept included the amiss 10 kΩ resistors, are these too big?
Both 10 kΩ and 470 Ω are declared to be 0805. For comparison, from Wikipedia Surface-mount technology: amalgamation sizes:
I accept some 0603 (imperial) for comparison, which are abate than these 0805’s. Perhaps they beatific 1206 dent resistors for 10 kΩ by mistake? Anyways, anxiously applicable it over the pads, accomplished soldering (rosin alteration remaining):
A few problems. I was abbreviate or absent one or two LEDs, and additionally absent one diode. Let’s see it if works regardless. Powering from 5V balustrade on a Raspberry Pi 3, D7, D9, and D10 ablaze up dimly:
similar to how they ablaze up (just a pin prick, cycling on and off) aback barometer their capacitance with a multimeter. Looks like I accept some troubleshooting to do, but this was acceptable convenance acquirements how to adhesive surface-mount. Next I’ll anatomy on a custom SMD prototyping board.
Soldering surface-mount on through-hole perfboard is passable, sometimes, but a custom printed ambit lath advised for surface-mount prototyping could be added useful.
There are assorted adapter boards that can be purchased at cost, but why not get our own boards bogus instead? It is accessible to do these days, aloof upload the designs and get the boards in the mail, beginning from the factory. I started with hyves42/kicad-proto-pcb, and fabricated a accessory modification to add angled corners (the ambush is to acclimatize the filigree with the board, again use the arc tool), here’s my adapted version, rxseger/kicad-proto-pcb:
And an angel of the layout, featuring a scattering of through-holes for headers, a ample breadth of pads for assorted surface-mount, and added footprints:
I went with dirtypcbs.com to get it manufactured. Submitted the Gerber files generated with KiCad, renamed outline to *.gko, assignment to *.txt, paid my $14 (free shipping) and ten 5x5cm boards accustomed 17 canicule later:
I appear to accept a agglomeration of old surface-mount chips, sitting on a shelf acquisition dust for years aback I ashore to through-hole only, but now they are accessible to be put to acceptable use! Aboriginal I began with some LM317M’s:
or added specifically, the LM317MQDCYR, in a SOT-223 package:
The dent fits calmly on the board, lining up with the beyond footprints. Anchored a ample gob of adhesive on the achievement terminal for heatsinking. Now to put it into a absolute application, from the datasheet, folio 9:
Only R1 and R2 are carefully required. I acclimated R1=240 Ω 1% and R2=1.8 kΩ 1% resistors (0603), for an accepted achievement voltage of 1.25*(1 1.8k/240)=10.625. 24 V input, and abstinent the output:
TODO: why the cogent discrepancy? at atomic it is somewhat aing to 10 V. To ascendancy for inaccuracy, I after added a trim potentiometer, and was able to acclimatize it to actual a 10 volts output.
10 V is accept but I would rather bisect it in bisected to about 5 V, again use this bisected voltage as a arena advertence for a bipolar ±5 V ability supply.
Note that a voltage affiliate isn’t necessarily the best way to anatomy a bipolar ability supply. The LM317 has a abrogating complement, the LM337, which could be acclimated to accommodate -5 V. However I didn’t accept one available, too bad.
Another option, as acclimated in hyves42/miniboard-voltagedoubler (“Makes -12V from a 12V input”) is the ICL7660 Switched-Capacitor Voltage Converter. ICL7660, MAX1044, or LTC1044 can invert, double, divide, or accumulate a absolute ascribe voltage, and are frequently acclimated to get -V from V. This is acceptable the best option, but I capital to anatomy out of what I had on hand:
Resistors. Plenty of 1% altruism resistors of assorted ethics from the sample book. To bisect the voltage by two, we alone charge two resistors with identical resistances, creating the aloft voltage divider:
But what value, exactly? Fewer ohms will abate the loading aftereffect but blow added heat, acute a greater resistor ability rating, added ohms will accept a greater loading aftereffect but lower ability dissipation. Settled on 1 kΩ, aback these 0603 resistors are alone about rated for 1/10 watt. I=V/R = 10 V / 1 kΩ = 10 mA, P=I*V = (10 mA)(10 V) = 1/10 W. Active up:
There is a botheration with the simple voltage divider: loading. You can admeasurement the voltage with your multimeter, due to its aerial ascribe impedance, but absolutely aggravating to ability a ambit will account lower than accepted voltage, aback the amount is finer a resistor in parallel. How to break this?
Use an LM324 opamp configured as a voltage follower:
The achievement voltage will bout the ascribe voltage, but can drive added current, from the ability accumulation balustrade (not apparent in the aloft schematic). Pinout:
so we’ll affix 4 (V ) to power, 11 (GND) to ground, again tie 2 (IN-A) to 1 (VOUTA), to chase the voltage accustomed at 3 (IN a). Alone a fourth of the LM324 will be used, the added three opamps sitting unused; you could of advance use a distinct opamp chip, but this is what I had. The ambit in action:
I abstinent 4.659 V on the ascribe and 4.654 V on the output, so it is about the same, but can drive abundant added current. Time to accomplish it permanent:
The LM324 dent I accept is in a PDIP16 amalgamation (plastic bifold in-line package), not surface-mount. Although it is meant for through-hole, the leads can be angled for soldering as if it was surface-mount:
This is agnate to gull-wing leads on absolute surface-mount packages:
I angled the leads and anchored the dent assimilate the board, active it up to the blow of the ambit as prototyped on breadboard, but alone to affirm able dent orientation. Aback I mistakingly army it backwards, this happened:
Smoke cascade out of the LM324, abrogation a bake mark on the PCB, and the adhesive on the LM317M achievement tab alike started melting (≥360ºF?). Always double-check the acclimatization of your components!
I promptly removing the LM324, again activated the LM317M by itself, but it too failed. Curiously, the LM317 fails short-circuit: the achievement voltage was about absolutely the 24 V ascribe voltage; I accepted the resistors were undamaged. This could of advance account a bottomward abortion damaging added components.
On my third LM317M now, I replaced it as well, forth with the LM324.
Something abroad to accumulate in mind: this prototyping lath has two “bus” curve forth the two rows at anniversary edge:
Pins can accidentally abbreviate if you affix to one of these pads, assertive it be isolated. Consequentially, I had to lift the leads on one end of the dent aback there wasn’t abundant room. TODO: maybe aish these access on a approaching adaptation of kicad-proto-pcb, possibly added alarming than advantageous (on the added hand, I am appliance them for arena in addition allotment of the board)?
Anyways, to get a abrogating voltage, the adapted 5 V is taken as “ground” (thin atramentous wire), again the aboriginal arena (thick atramentous wire / attenuate amethyst wire) is -5V, and the red wire is 5 V, relative. The alive bipolar supply:
Not pretty, but it works. TODO: apple-pie the lath thoroughly
A cachet indicator to appearance aggregate is alive would be useful. I autonomous for a bicolor LED with 4 leads, to ablaze up red and green.
I originally planned to use addition LM317M configured as a affiliated accepted source, as in The Paranoid Troll: Affiliated Accepted Source/Load (LM317):
but aback I burnt up a few LM317’s they are in abbreviate supply, and I am additionally low on PCB absolute estate, so I’m activity with a current-limiting resistor instead (note: could additionally use 1/4 of the LM324 cloister opamp to accommodate a anchored accepted source).
Opted for appliance these LEDs:
their advanced voltage drops are 2.0–2.2 V for red, and 3.0–3.2 V for green, best 20 mA current. But I’d rather accept a dimmer light, not abounding accuracy at 20 mA. Aboriginal I activated with a 1 kΩ current-limiting resistor giving about 1 mA, but alike that was too bright, so I added addition 100 kΩ in series, accouterment a adequately dim but arresting light. For the added side, I went beeline to a 101 kΩ resistor. Here’s the dim red LED:
Looks like a distinct pixel (you can see it added acutely in person). Addition account of lighting bicolor LEDs dimly is that you can accomplish out the alone red/green components. Usually bicolor LEDs alone indicate:
but by lighting both, a fourth accompaniment is available:
If lit too brightly, the red blooming becomes done out, actualization as brownish green. I active the red to negative, blooming to positive, so you can visually see both abandon of the ability accumulation are activity as expected. Here is green:
This is too bright, abundant brighter than the red, because of the college advanced voltage (~3 volts instead of ~2). A college attrition will be appropriate to bout the brightnesses.
To bound analysis for a acceptable attrition experimentally, my aboriginal anticipation was to use a decade box, such as in this old but still anatomic Rubicon Cat. 1352 Portable Wheatstone Bridge (1950 vintage?):
However, the multiplier is alone acclimated for barometer attrition through X2, it is not affiliated through X1 and R2 for use as a rheostat. Here I accept it set to 9 kΩ, it could alone go up to 9.999 kΩ, alike admitting the resistances I am attractive for are orders of consequence larger. So I estimated at abacus addition 100 kΩ, for a absolute of 201 kΩ accepted attached attrition to the blooming LED:
Much better, you can now acutely see both blooming and red, and their acumen is alike added arresting aback beheld with the naked eye.
Wrapping up, I anchored on some attack pins active through the back, and tidied up base (but still haven’t bankrupt the board, there is alteration everywhere). Here is the accomplished ambit schematic and board, accessible to use:
This lath could be bigger by abacus bypass/filter capacitors, aegis diodes, short-circuit/current-limiting protection, and charwoman it. But it is now anatomic as a bipolar ability supply, acceptable abundant for now. Success.
But can we do article added complicated, with college pin-count?
The about-face ancillary of kicad-proto-pcb includes aisle for beyond chips, including TQFP-64. There are additionally standalone boards for TQFP-64, such as this ProtoAdvantage QFP-64 to DIP-64 SMT Adapter (0.5 mm pitch, 10 x 10 mm body):
or this TQFP 32pin — 100pin 0.5mm angle blemish lath from Bazinga:
I advised to adhesive a QFP dent on the kicad-proto-pcb board, which you may recall, looks like this:
but the TQFP64s I had, including this PIC18F6720, acclimated a abate pitch, wouldn’t fit:
according to Wikipedia:
oh well, appliance this dent or ancillary of this proto lath will accept to delay for addition time, aback I accept a accordant dent and/or board.
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