No, well, sort of no. Gerbers are files that describe a PCB’s various layers (copper, silkscreen, mask, etc.) mainly intended for upload to a fabrication facility.
You could I guess use a Gerber viewing application to create an image of the copper layers which you then might be able to use to make a mask for PCB etching. That’s a bit roundabout, though, since the EDA that created the Gerber files could presumably make images of the copper layers directly.
In the case of the VCO you appear to be referring to, images for (2 layer) etching can be found on the MFOS page:
(about 3/4 of the way down)
But I guess if you’re just getting started with PCB etching, this would not be a good one, you’d want to get good at doing single layer boards first.
It’s a (slightly annoying imo) way to draw a potentiometer configured as a “variable resistor”, where one side is connected to one end of the potentiometer track, the other side connected to the wiper (and ideally also to the other end of the track).
Drawing from here, which has a bit more on the basic potentiometer configurations.
It is a NTC thermistor, a temperature variable resistor. It is used to compensate temperature changes to keep the oscillators frequency stable. You could also replace both resistors by 4.7*2.2/(4.7+2.2)~=1.5k but as I said frequency won’t be that stable over temperature changes. If you use a NTC resistor make sure to keep it as near as possible to your transistors or even use thermal paste to connect them.
@analogoutput covered most of it. Gerbers are for board houses and not directly useful for DIY PCB’s. You can use a gerber viewer to generate printable artwork from the gerbers - but if you have access to the original designs it’s usually easier to just print the layer directly from your EDA. Though this may take some experimentation to get the scaling right with some EDA’s and some output formats.
With KiCad I found exporting as SVG usually resulted in a loss of scaling and was a pain to get scaled correctly for printing. But using the “plot” command you use to generate gerbers and generating them as PDF’s instead of gerber format worked well and preserved scale. (Though again plotting as SVG wound up with the scale being slightly off when I’d try to print them.)
The other trick is for DIY etching you usually want an inverted and mirrored version of the copper artwork. Though - that depends on the etching method you’re using. Toner Transfer vs. UV exposure may require different settings. I strongly recommend picking a design with some text on it so you can confirm before etching that the right parts are masked and things are facing the right direction.
If you have access to gerbers but not the EDA source (which is fairly common for DIY modules it seems. A good number of people share gerbers but not the original files.) or they’re from an EDA you don’t have access to then using a gerber viewer will usually let you isolate the copper layer you need and invert/mirror it if necessary and then print it out. Kicad has a decent gerber viewer built in but there are lots of them out there. Even some that are web-based.
I’d like to know a bit more about getting panels made by the board houses. Are there different settings that need to be used when you submit them (thickness/materials/???), or do you just submit them as if they were a normal PCB and everything turns out fine?
You could change thickness to 2.0mm, but that will usually cost you a leg !
(I mean, it’s less than $10 for 5x 10x20cm panels in 1.6mm, but there is a $35 additional fee for getting them in 2.0mm at JLCPCB…)
Color is up to you. You can only choose the soldermask color, the silk-screen color will be white or black for maximum contrast.
Also, depending on your health consideration, you may select the lead-free finish, for an additional fee.
I don’t as it will be hidden behind knobs and jack washers. I wash my hands after assembly and that’s it for me.
You should look up at the fab-house you’ll intend to use how to get rid or specify the location of the order number, or they’ll put it where they see fit, and that may be in the middle of the panel !
(At JLCPCB, getting rid of the order number costs an additional $1.5, that’s affordable…
But you can specify a location at the back of the panel for free. Just add a text with exactly JLCJLCJLCJLC on the back side silk-screen and check the “Specify a location” check box when ordering)
Last step, add something like “This is a front panel, there are no electrical circuits on it, no need to make electrical tests” in the comment section.
(All these were shared by @analogoutput somewhere on this forum…)
Also be sure to shop around if you’re getting boards made. JLCPCB has some great deals - but for some sizes other places may be better. Like how @analogoutput got his little adapter boards done at OSHPark cheaper. OSH used to be my go-to as they were one of the first low cost options - but they were REALLY slow. That’s because all of these low cost options work by batching together a lot of small orders into one big panel they then cut up and re-sort into individual orders. Since board houses aren’t really setup for small one-offs and are optimized for doing big batches of boards. But as OSH got more popular their turn-around times got quicker and quicker since orders came in fast enough they could get full panels done quicker.
Then the board houses themselves saw how they were missing out on the small stuff and started offering their own low cost prototype services that worked similarly. Now there are dozens of options. https://pcbshopper.com/ lets you compare prices from 21 different manufacturers. Though - that’s just price…you should still research quality/reputation/speed of the services.
For boards like we use there aren’t a ton of gotchas to watch out for. But - it’s still important to watch the design rules to make sure you don’t try to do something the board house can’t. And there are all kinds of ways that can get confusing and tricky. EEVBlog has a few videos on it. Here’s one from a few months ago with a few good tips on avoiding problems:
But do a search for PCB on his channel and you’ll find all kinds of great tips and info about how boards are made and things to watch out for when doing designs.
But again - we’re not dealing with super tiny traces/clearances (even the SMD parts used on some modular boards like the nlc and mutable designs are “big” enough to avoid a lot of potential issues.) And we’re not dealing with high speed digital logic or RF or other “complex” circuits where things can get tricky fast.
If you’ve got a set of gerbers that are known to be good then it’s really pretty simple to just upload them to the board house - pick the options you want and order. Though as @eric points out the cheap prices are usually based around standard options and small changes like heavier copper or thicker/thinner boards can suddenly cause the price to skyrocket.
I forget if you mentioned or not if you were a pedal diy person. I’ve seen some pretty comprehensive designs on effectslayouts.blogspot.com, perf board as well as for etching. Any experience with those designs?
Haven’t done any pedals. My guitar skills are really poor and the last time I considered trying to do some pedals I didn’t have the money for cases buttons and knobs. One of these days I need to look into that again…but unless I suddenly get a lot better at guitar it won’t be very soon
Meh. A gentle challenge. I’m intrigued to know more about this oscillator but always pause when im just seeing stripboard layouts. That said if this works (and I see it here :)) then I will build it too.
The XR2206 can do both VCO and VCA since it has a multiplier inside. The VCO response is tricky though because it is exponential for positive voltages but linear for negative voltages. It is possible to get 20 - 20k sweep but shaping the control to a good 1V/oct is going to be hard without the help of a look up table.
If I have 1k NTC can I use that same formula to back calculate R10-12? I’ve never found a good explanation of how they ended up with this configuration or values…
And any explication of the dual match transistor pair vs a single pair
Sure as long you have the same total resistance as R10-R12. Tracking over temperature changes might be not as good. I think important is ratio of fixed to temperature variable resistance. If you are not getting it into scale try to fiddle around with R13 in small steps, eg. 10 ohms. Kassutronics and René Schmitz got some more information on that topic:
Maybe I’m getting your question wrong but you either use a matched pair of 2N3904s or one BC847BS. I have very good results with the BC847BS and not that good results with the 2N3904s. But maybe this relates to poor matching. I choose the BC847BS because it’s cheap and results are good although it’s SMD and a bit fiddly.
Edit: This was always meant as a PCB project, I wanted to have both options available. That’s why it is in the schematics.
