• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Understanding TRS schematic and pull-up wiring

Not open for further replies.


New Member
Hello everyone, I'm a beginner to electronics and have a question I haven't been able to solve with Google, thank you in advance for reading this.

Very briefly, the main goal: I'm a musician and am trying to make a simple small box that converts an analog expression pedal to MIDI messages. I'm good on the programming end, but need a little help making sure I connect things correctly.

I'm trying to modify a project I found online, and the creator helpfully uploaded a schematic showing the internal wiring, but I'm having trouble figuring out to translate this into physical reality. I'm uploading the schematic in this post.

Referring to the inputs with green on the left, his description says roughly this: "Unfortunately I couldn't find a TRS that had a switch on the Ring connector at my local electronics store so this pulls the analog pin on any unused expression pedal socket to VCC instead of ground: this is needed to prevent the pin's voltage from 'floating' and generating garbage messages. You have to pull it to one side or the other when not in use."


I understand this basic concept of a pull-up, but don't understand how I'm supposed to wire it: it seems like this connection to VCC won't be made when a pedal is plugged in? The stereo input jacks I purchased have four areas where I can connect wires (maybe it's TRRS and not TRS, I'll have to check), but basically I don't understand what the green wire in the schematic and the arrow it attaches to are. I would very much appreciate any help you are willing to offer.

Here's the link to the original post if you're interested, and again, I thank you for your patience and hope you are having a great day. http://www.dsprobotics.com/support/viewtopic.php?f=3&t=1859
Last edited:
Not open for further replies.

Latest threads

EE World Online Articles