# Arachnid Builds (Older Version)



## Cybercow (Jul 8, 2019)

*Arachnid Build September 2018 - July 2019*

The Arachnid is an FV-1 effects processor chip based building platform PCB from PedalPCB. It is JUST the PCB and requires the FV-1 and a couple other specialized ICs to complete. The new 2019 version does NOT use the ATTINY85 analog pot encryptor, instead it uses a SP8T rotary switch with a diode selection matrix to select from 8 the programs loaded into the 24LC32A EEPROM (also required). I bought last years’ version which utilized the ATTINY85 encryptor IC and an B100K pot to select the programs. But I did not want to use that method and seeing as I bought 3 of the older Arachnid build platform PCBs, I went about tackling the process of modifying the build to accommodate an NOS Grayhill miniature, military grade SP8T rotary switch. Tommy Riebel helped out by creating the daughterboard PCB to mount the rotary switch and the 9 x 1N914 diodes with wiring outputs to connect to the main PCB where the ATTINY85 would have gone. Basically, I wanted a rotary switch with detents as the program selector instead of the fuzzy-logic of the ATTINY85 and analog sweep of a B100K program selection option.

The instantiation of the daughterboard presented a stuffing problem in that it would NOT fit in place of the now omitted B100K program selection pot - all the pots are PCB mounted. To circumvent the stuffing problem, I found that SmallBear’s 5-Pot daughterboard left a space precisely where the selection switch needed to go. I found that with the pots mounted on the SmallBear 5-pot PCB, the switching PCB daughterboard cleared the underside of the 5-pot PCB my about 2mm, so that would work. I then double-checked the remaining space required by the main PCB and found there was enough depth clearance to mount it a few mm above the 5-pot daughterboard and still leave room for the stompswitch. There was even enough space to cram a 9v battery beneath the main PCB if I so chose, but I don’t accommodate batteries in my builds, so I went forward without further consideration. So, instead of mounting 16mm pots on the main PCB, I went with 9mm pots mounted to the SmallBear 5-Pot PCB daughterboard and wired the 5-pot daughterboard to the main PCB.

I could have mounted the 1/4” jacks on the sides of the 125B enclosure, but I wanted top-mounted 1/4” and DC jacks. After several sessions of pencil, paper, measuring implements and actual measuring, component placement testing and board-stuffing drills, I was able to get just what I wanted in a 125B enclosure. I had to use an “outtie” (external nut) DC jack to secure the precious space requirements of securely and in a non-shorting (non-touching) required. It felt very much like planning a game of Tetris.

Over the last 10 months I planned, measured, sorted out the mods required for the main PCB (what to leave out and where to add the new connections. Meanwhile, Pedal PCB has since release toe 2019 version of the Arachnid build with utilizes a commonly found SP8T rotary switch that mounts directly to the main PCB; along with the other 5 pots needed to actuate all the control features of the build. Essentially, I redrew the schematic to accommodate my changes and as it turned out, my changes are precisely what PedalPCB did to the newer version. Had I been paying attention to the PedalPCB forum, I would have learned sooner that the Arachnid build platform had been modified to do precisely what I wanted to do in my builds with the older version of the PCB. I could have saved myself a lot of time and enjoyed the builds much sooner.

All that being said, I present the unfinished enclosure older version of PedalPCB’s “Arachnid” build. Having procured 3 of the PCBs with FV-1, I also acquired 3 different EEPROMs to go into them for programs. I got the ‘Module8’, the ‘Octagon’ and a third customized EEPROM with my own selections of the several available for a custom EEPROM. I also learned that more programming options are coming.

Before I finish the enclosures, I am going to exact one more modification to each of these 3 builds. The FV-1 has a set of “default programs” inherent within the FV-1. I will add a toggle switch near the top where I’ve already measured a subminiature SPST toggle can fit. It will connect directly to pin 13 of the FV-1 to pull down the logic selection of that pin to access the internal program patches.

All three of these are now tested and sound great. Am so looking forward to new program patches for these puppies.

And now, onto the journal of photos and some circuit porn (the last photo shows the schematic mark-ups for what to exclude in the build to accommodate the custom daughterboard) . . . . .


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## phi1 (Jul 8, 2019)

Wow that's impressive! Bummer you had to take the long way around, but hey it's more gratifying that you figured it out! I have the old version with the pot and i agree it isn't ideal. 

One small suggestion, I also put a switch for the internal rom programs. Instead of soldering onto pin 13 of the fv-1 (which is totally doable) I looped a wire around the leg of the resistor under the eeprom chip. The right leg of that resistor goes to pin 13 anyway. Check for continuity to make sure I'm right haha. Might be a bit easier.


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## Cybercow (Jul 9, 2019)

phi1 - thanks for the kudos. As for the internals toggle . . . . I'm not physically tying to pin 13 of the FV-1. I'm doing precisely as you've suggested. When I installed R5, I looped the right lead up a tad so there is room to slip the tip of stripped wire beneath it and curl back upward for a solid connection, without soldering onto the FV-1 itself. I didn't think to take a shot specifically of that aspect, (and if you look carefully at the first photo in the OP you can see it, but here it is . . .


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## caspercody (Jul 9, 2019)

Will you be selling these boards? I would need one set


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## Cybercow (Jul 9, 2019)

caspercody said:


> Will you be selling these boards? I would need one set



CasperCody - SmallBear has the 5-pot daughterboards and the rotary switch daughterboard was made specifically for an NOS "Grayhill" switch; which is an uncommon component to find. I found those Grayhill rotary switches on eBay and that vendor is now out of them. I only got 3 of them to do these 3 builds. If you really want that rotary switch daughterboard, it's an OSHPark file and I can share that if you really still want it.


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