Logic Analyzer - frustration connecting to DUT - Page 1
Forum section: electronics / beginners

author: davegravy
author_rank: Regular Contributor
timestamp: March 09, 2024, 01:34:08 am
content: I'm tearing my hair out trying to connect several channels of my logic analyzer. I have a SBC with male headers and a shield with male headers, and dupont cables between them.My analyzer came with these minigrabbers:https://digilent.com/shop/mini-grabber-test-clips-with-leads/I can clip the mini grabbers to the underside of the male headers (the solder joint side) but they pop off with the slightest movement and I can only get one or two connected at a time.It would be great if the dupont cables came in a Y variant, but I can't find any beyond paying $3 per custom cable from Etsy:https://www.etsy.com/listing/1333156495/dupont-y-cable-splitter-jumper-wire-maleI could DIY a bunch of these but I figure there must be a standard way of doing this, something common and OTS I can buy.How do people usually connect their analyzer in these cases?

author: ataradov
author_rank: Super Contributor
timestamp: March 09, 2024, 02:00:42 am
content: For the mini clips there is a world of difference between cheap junk (like what you've got) and good quality ones. The quality grabbers I use are Tektronix KlipChip SMG50. I don't think they make them new, but there are some on eBay. They are expensive, but easily some of the best piece of test equipment I bought.They have a very long thin neck, so you can grab at the base of the male header and there will still be enough length left to connect the female part. It will not be the most strong connection, but it is better than grabbing from behind. And they are perfect for reaching to the inner part of the dual row right angle connectors.Thishttps://www.amazon.com/10PCS-Grabber-Jumper-Analyzer-Colors/dp/B083PRVPCR/ref=pd_bxgy_q_img_d_sccl_1/136-0169385-0517600looks like a modern recreation of those grabbers, but Amazon price per grabber is basically the same as the original Tek ones. I bet they are cheaper on Ali though.

author: davegravy
author_rank: Regular Contributor
timestamp: March 09, 2024, 02:06:42 am
content: Thanks, bought.

author: tooki
author_rank: Super Contributor
timestamp: March 09, 2024, 09:14:25 am
content: FYI, one model of clip in that style that I really like is the Hirschmann/SKS Micro-Kleps:https://www.sks-kontakt.de/en/test-measurement/products/product?nr=9739721The non-obvious thing about these is that the contact hooks themselves can be rotated by turning the round plunger, allowing them to squeeze into spaces where a rigid style can run out of room for the connecting leads. I just wish they made them in more colors!These are a top-quality product, and can be expensive if you don’t know where to look. Reichelt.com has the best price I’ve found for them so far, by far. (Everyone else charges around $11 apiece, Reichelt under $4.50! So it only takes a few pieces to make it worth spending the shipping cost.)Also: The set on Amazon claims to include silicone DuPont jumpers. If that’s true, that is a really nice feature. I’ve spent a fair bit of time making my own silicone DuPont jumpers because they weren’t available at the time. (There are now some vendors selling them.)

author: Ian.M
author_rank: Super Contributor
timestamp: March 09, 2024, 09:36:47 am
content: Take some veroboard, cut off a strip with five holes on each track (or use one of those proto PCBs that mimic a solderless breadboard) and solder in three male SIL headers with a one hole gap between them so their corresponding pins are in parallel. You've now got a breakout board that you can place between the SBC and the 'shield' using extra F-F duPont wires.

author: davegravy
author_rank: Regular Contributor
timestamp: March 09, 2024, 01:57:51 pm
content: Quote from: Ian.M on March 09, 2024, 09:36:47 amThis seems really elegant. I'd be tempted to leave out the gaps on a few rows and use these for ground references since I'm always running out of those

author: RoGeorge
author_rank: Super Contributor
timestamp: March 09, 2024, 02:08:15 pm
content: LA probes were not meant to be connected on the pins soldered side of the PCB.Pull out the shield a little, and connect the LA probes in the space between the SBC and the shield. Alternatively, clip the probes to the IC pins, or solder extra wires if nothing else works.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: March 09, 2024, 05:35:58 pm
content: If you have access to the bottom of the board, which you seem to have since you tried to attach your grabbers there, then I would just solder a second header to the solder joints of the existing header. Forget about the grabbers and plug the flying wires directly into this header. Takes three minutes and gives rock solid connections.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 11, 2024, 08:35:17 am
content: Mini grabbers come in a whole lot of different qualities, and those shown from "Digilent" are among the most atrocious, while those others (Ataradov) look "decent", but I don't have that particular model. And even with very high quality grabbers (I've seen very high quality super mini grabbers from some Japanese brand, I think they cost EUR12 a piece...)As an alternative, you can also take a standard male IDC header and clamp or (hot) glue it to the PCB itself, and then use 0.2mm enameled wire to make the connections between the pins and the IDC connector. In the IDC connector, you can then use Dupont wires, or just a simple (short) flat cable.The big thing here is gluing (or clamping) the IDC to the PCB. This prevents any relative movement, and thus there is no extra stress on the wires.For a "less permanent" solution, you can also solder two male IDC headers together (For example a straight and a 90 degree version and clamp that to the PCB. Then you can use the test clips between this header adapter and the test points. Similarly, you can also both mount the PCB and the logic analyser on a piece of corrugated cardboard (plywood, etc) to prevent relative movement of fragile connections.