FreeCAD News

It feels fit­ting to write a KiCad relat­ed sto­ry this week as KiCon Europe is cur­rent­ly under­way in Bochum Ger­many. We send best wish­es to our KiCad friends and col­leagues and hope they are hav­ing a won­der­ful time.

Mean­while, in Liv­er­pool UK, there’s a great Fri­day night social bike ride com­mu­ni­ty where peo­ple get togeth­er and, well, ride bikes. 

In an effort to extend the com­mu­ni­ty rid­ing into the dark­er sea­sons there’s been copi­ous use of Neopix­els. In fact, the sub­ject of this Forged in FreeCAD, Adri­an from MCQN Ltd is the cre­ator of the WLED based, “My Bikes Got LED” kit which makes adding and cru­cial­ly pow­er­ing, Neopix­el strips to bikes easy.

With the light­ing some­what cov­ered anoth­er inter­est­ing chal­lenge for group rid­ing was a group sound sys­tem, they like to play music with a playlist being streamed from a phone to some pow­ered portable speak­ers. This obvi­ous­ly has to cov­er a range of dis­tances with 40 plus bikes stretch­ing out to form a long group, beyond the range the Blue­tooth can reli­ably provide.

The work­ing solu­tion has been to use a wire­less micro­phone trans­mit­ter and receiv­er unit, mount­ed atop a self­ie stick to con­nect the front run­ning pow­ered speak­ers to the ones at the back of the pelo­ton! Not want­i­ng to risk his nice Rode set to Selotape and zip ties Adri­an used FreeCAD to whip up a nice pair of action cam­era clamp com­pat­i­ble cas­es with cut outs for all the access and cabling.

How­ev­er, the solu­tion wasn’t per­fect. The micro­phone trans­mit­ter is, well, built for a micro­phone input, not a line lev­el input that the front run­ning speak­ers can out­put. Some atten­u­a­tion was need­ed or else the audio sup­plied to the rear of the group ride sys­tem could well be dis­tort­ed. A pret­ty straight­for­ward atten­u­a­tion cir­cuit can be made which is sim­ply a vari­able resis­tor and a cou­ple of capac­i­tors to block any DC cur­rent. A pro­to­type was quick­ly lashed togeth­er and test­ed and was deemed to be an ade­quate solution.

Around the time that FreeCAD 1.00 was released, Adri­an was work­ing on this cir­cuit and thought it might be a great idea to check out some new FreeCAD fea­tures, as well as con­sol­i­dat­ing the cir­cuit onto a prop­er cir­cuit board. KiCad made quick work of the cir­cuit design, but Adri­an had some par­tic­u­lar poten­tiome­ters left over from anoth­er project which didn’t have a KiCad footprint. 

For those who don’t know, a KiCad foot­print mod­ule includes the com­po­nent out­line, per­haps some silkscreen draw­ings and mark­ings to help you place the com­po­nent, cop­per pads and holes and more. Option­al­ly a more com­plete foot­print in KiCad also has a ref­er­enced 3D mod­el. This means that you can not only make nice ren­ders of your PCB and com­po­nent assem­bly, but can be incred­i­bly use­ful when check­ing phys­i­cal clear­ances when design­ing an enclosure.

If you are mak­ing com­po­nent mod­els in FreeCAD for KiCad foot­prints, then there is the excel­lent KiCad StepUp work­bench which has an incred­i­bly use­ful set of tools. Using the KiCad StepUp work­bench you can import kicad_mod files into FreeCAD (the com­po­nent foot­print files) and then cre­ate per­fect align­ment for your 3D com­po­nent mod­el before export­ing back to your local KiCad libraries. 

You can also load KiCad PCB lay­outs and parts into FreeCAD and to mod­el to, or indeed to con­vert to STEP or IGES files for fur­ther processing.

With his poten­tiome­ter mod­el and KiCad foot­print set­up, Adri­an con­tin­ued to use FreeCAD and KiCad in com­bi­na­tion to mod­el his iter­a­tions of enclo­sure. Load­ing up the KiCad project in FreeCAD as a STEP file, Adri­an could then use the Shape­Binder func­tions to be able to use the KiCad PCB geom­e­try as ref­er­ence in his enclo­sure design. 

Adri­an also dived in to explor­ing the (then) new Assem­bly work­bench and through all these tech­niques mod­elled a real­ly well-fit­ting enclo­sure for a 3D print. We think the results and the process look great and cer­tain­ly more robust than the sol­dered to a bit of Ver­oboard prototype!

As we write this post, it’s inter­est­ing to note there are a few con­ver­sa­tions around com­bined KiCad and FreeCAD use. Over on Hackaday.com, Arya has doc­u­ment­ed their adven­tures in learn­ing FreeCAD for PCB enclo­sure design. And in the com­ments, we can see Elliot, the Hack­a­day Man­ag­ing Edi­tor, dis­cussing using the shape binder tech­niques that Adri­an has used here. 

It’s great to see peo­ple dis­cussing these approach­es. Final­ly, and also relat­ed, we spot­ted over on Mastodon this week that Mor­gan is active­ly work­ing on KiCon­nect, KiCon­nect is anoth­er FreeCAD work­bench which offers exten­sive push and pull between KiCad and FreeCAD, so for exam­ple it’s pos­si­ble to move a board edge in KiCad and have your enclo­sure design respond around the changes in FreeCAD! Excit­ing stuff that’s cer­tain­ly worth keep­ing an eye on.

Thanks to Adri­an for tak­ing the time to talk to us about this project. The audio shifter, as well as many oth­er designs from Adri­an, are OSHWA cer­ti­fied and the repos­i­to­ry for this Audio Lev­el Shifter project is here.