Author Topic: Breadboard Test Leads  (Read 4021 times)

0 Members and 1 Guest are viewing this topic.

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Breadboard Test Leads
« on: June 28, 2022, 10:36:22 pm »
A couple of months ago, designed some custom test leads for a solderless breadboard. They are 4mm Banana plug to male Dupont 2.45mm test leads. They are perfect for connecting a multi-meter or power supply to a solderless breadboard.

I am having the test leads custom manufactured and I’m reselling them on my project’s website.

I would like some feedback on this idea before I invest too much money into it. Thanks

Project Website: https://www.pitronllc.com

___________________________________________________________________________________________________________________________________________________________________
Update:

 I decided to turn Rev2 Banana Breadboard Test Leads into an Opensource Project.

This project is licensed under Attribution-ShareAlike 4.0 International (CC BY-SA 4.0). https://creativecommons.org/licenses/by-sa/4.0/

Once the design is complete, I will register this project with Open-Source Hardware Association. https://www.oshwa.org/

Also, I plan to upload the final design files to GitHub. https://github.com/PitronLLC/Pitron_Banana_Breadboard_Test_Leads
« Last Edit: July 15, 2022, 11:45:04 pm by Pitron »
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 11537
Re: Breadboard Test Leads
« Reply #1 on: June 28, 2022, 11:17:22 pm »
Your design puts a lot of leverage on the duPont pin, which if its the crimp type isn't particularly robust, and on the breadboard contacts, which is why I and many others who have made something similar prefer to use much thinner and more flexible wire.   Personally I use 3" extension adapter cables that fit over my ordinary DMM probe tips with duPont pins on the other end.  If anyone is looking to DIY themselves, the female Molex 5 1/4" drive power contacts fit nicely over most meter probe tips.  Discard the shell and use heatshrink to insulate.
 
The following users thanked this post: Someone, Pitron

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #2 on: June 29, 2022, 01:33:28 am »
Hi Ian.M, thank you for your reply.

The heads of the test leads are made of steel needles specially used for injection molding. They are more robust than the regular DuPont pins. DuPont pins are 0.65mm in diameter, the test leads are approximately 0.8mm. They fit perfectly in a breadboard and I haven’t had any issues with them bending. 

I agree that I should use a thinner wire.

I am planning on designing a second revision of the breadboard test leads. On the new design, I’m going to use a smaller wire gauge (20 or 22 AWG). I’m considering changing the wire material from PVC to silicon. Since silicon is more flexible and easier to work with.

Also, do you think $17.98 is a reasonable price for a set of test leads?

Thanks again for your feedback.
« Last Edit: July 15, 2022, 02:48:33 pm by Pitron »
 

Online tggzzz

  • Super Contributor
  • ***
  • Posts: 16127
  • Country: gb
    • Having fun doing more, with less
Re: Breadboard Test Leads
« Reply #3 on: June 29, 2022, 09:42:33 am »
Also, do you think $17.98 is a reasonable price for a set of test leads?

I have no comment on the general design, since I loathe solderless breadboards.

However, there is a general point about pricing: what's the cost of achieving similar objectives by other means?

In this case my first port of call would be a standard (i.e. cheap, multisourced, and maybe already available) lead with a banana plug on one end and a small croc clip on the other. I'd attach the croc clip to an offcut of wire or component lead.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 
The following users thanked this post: Pitron

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 11537
Re: Breadboard Test Leads
« Reply #4 on: June 29, 2022, 12:28:28 pm »
For price comparison, see what Walmart can do for your price-point:
https://www.walmart.com/ip/Meterk-Multimeter-Test-Leads-Kit-21PCS-Digital-Electrical-Probes-Set-Alligator-Clips-Mini-Grabber-SMD-IC-Hook-Electronic-Lead-Kits/784565904

If your customers are price-sensitive you've already lost.  :(
 
The following users thanked this post: Pitron

Offline RogerThat

  • Contributor
  • Posts: 45
  • Country: se
Re: Breadboard Test Leads
« Reply #5 on: June 29, 2022, 01:13:37 pm »
For powering breadboards I have two of these cables, works perfect.

edit: I think your cables are too bulky, if you put them in the holes next to each other they will probably not go in straight?
I usually use the power rails on the breadboard, so no need to have the +- separate. When I want to measure something I use the multimeter tips directly on the components alternatively a small hook on a short jumper wire.
« Last Edit: June 29, 2022, 01:19:20 pm by RogerThat »
 
The following users thanked this post: Pitron

Offline MikeK

  • Super Contributor
  • ***
  • Posts: 1068
  • Country: us
Re: Breadboard Test Leads
« Reply #6 on: June 29, 2022, 01:24:41 pm »
What RogerThat shows is exactly what I do too.
 
The following users thanked this post: Pitron

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #7 on: June 29, 2022, 04:25:53 pm »
Thanks for all the replies.

I’m going to work on lowering the price of the test leads. The reason the price is so high is because I put in a small order which caused the over all price per set to increase.

Hopefully, on my next revision I’ll be able to put in a larger order which will bring the cost per set down to a more competitive rate.

RogerThat, your cable is very similar to the cable I started out with. Ill test my cable to see how well it works when I put both of them in a hole next to one another.

Also, does anyone have any preferences on the length of a test lead? The average length seems to be about 1 meter.

Thanks again for all the feedback. I am still in the learning stages of this project and all your opinions are very valuable.
« Last Edit: June 29, 2022, 04:32:44 pm by Pitron »
 

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #8 on: June 29, 2022, 05:21:12 pm »
Hey RogerThat,

I just tested the Test Leads, and they seem to both fit in the holes next to one another (it’s a snug fit). The molded strain relief is flexible, which helps out a lot.

I’ll try to redesign the molded strain relief, to make in thinner and less bulky. The only issue is that ill have to order a new pressure mold. I’ll talk to my manufacture about it.

Also, does anyone think 9-10 dollars is a good target price?

Thanks again everyone.

 

Offline viperidae

  • Frequent Contributor
  • **
  • Posts: 306
  • Country: nz
Re: Breadboard Test Leads
« Reply #9 on: June 29, 2022, 09:57:50 pm »
Can't say I'm a fan of websites advertising a standard price as a "sale"
In some countries, mine included, that is considered misleading advertising.

I would be concerned about the weight of those probes bending the spring contacts in the breadboard
 

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #10 on: June 29, 2022, 10:14:19 pm »
Hey Viperidae

When I originally launched the test leads the price was $21. I lowered the price do to lack of sales. I understand how that could be miss leading, so I removed the sales banner on the website. :)
 

Online tooki

  • Super Contributor
  • ***
  • Posts: 8626
  • Country: ch
Re: Breadboard Test Leads
« Reply #11 on: June 29, 2022, 11:58:23 pm »
While I don’t revel in piling onto the criticism, and I absolutely do not want to discourage you, you did ask for feedback, so here goes:

 
A couple of months ago, designed some custom test leads for a solderless breadboard. They are 4mm Banana plug to male Dupont 2.45mm test leads.
Sorry what?
Do you mean 0.1” (2.54mm) pitch? Your cables do not allow for a 0.1” pitch, the grips are much too big. Pitch is the spacing between pin centers.

DuPont pins are 0.65mm in diameter
No. They are square, 0.025” (0.635mm) on each side.

the test leads are approximately 0.8mm. They fit perfectly in a breadboard and I haven’t had any issues with them bending. 
The diagonal of a 0.635mm square pin is about 0.8mm, but when you insert those into a breadboard (which is already at the outer limits of what goes in them comfortably: on expensive breadboards they can be tough to insert, on cheap breadboards it stretches the contacts), you’re not doing it at a rotation where the diagonal is perpendicular to the contact axis.

Upshot is, if you’re designing something expressly for breadboard use, I’d shoot for 0.5-0.6mm diameter, and it needs to have tapered points or you’ll never get them in. (I’ve encountered Chinese breadboard jumpers with 0.5mm round steel pins, which would be great if they were tapered, but they’re not, so they often just snag.)


I agree that I should use a thinner wire.
I am planning on designing a second revision of the breadboard test leads. On the new design, I’m going to use a smaller wire gauge (20 or 22 AWG).
Why so huge? Breadboards aren’t intended for huge currents. 24AWG is more than enough, comfortably.

I’m considering changing the wire material from PVC to silicon. Since silicon is more flexible and easier to work with.
Well, silicon is a hard, brittle element. It’s not flexible in the slightest. ;) You mean silicone, and indeed I do prefer using silicone wire for breadboards. But more important than the insulation material is the wire stranding: 24AWG stranded wire can have as few as 7 strands and as many as 128 (like Kabeltronik LiFY). This makes a massive difference in how compliant and limp a cable is. Not all silicone wire is made for flexibility. Also bear in mind that silicone has inferior abrasion resistance than PVC, and the surface tends to hold onto dust. So a super fine stranded PVC may be superior in some respects. I’d take that over low-grade silicone wire any day. The good Chinese silicone 24AWG I mention later has somewhere around 40 strands.

Also, do you think $17.98 is a reasonable price for a set of test leads?
If it’s a top-quality product in every respect then that is reasonable. (Top quality banana plugs cost $2-3 apiece, so that gives a sort of context. Hirschmann, a top-quality German manufacturer, sells a banana to female DuPont cable, made with ultra fine stranded 24AWG wire, for around $6-7 apiece. They don’t make one with male pins at all, alas.)

Have you measured the contact resistance of your cables? Cheap banana plugs often do poorly here, so that’s one thing you wanna check yours for. (Another is longevity: do the lanterns weaken over time? Cheap ones do after a few hundred insertions, whereas a Stäubli or Hirschmann lantern plugs remain as good as new even after decades of use. I have some that are likely 30+ years old and still work like new.)

I’ve attached some photos of a few cables I’ve made for breadboard use: the one with the banana plug is a 0.8mm pin intended for high-density D-sub connectors (like the HD-15 used for VGA). Even with the lovely torpedo-shaped point, they are quite difficult to insert into a 3M breadboard. Those pins aren’t intended for individual use, so I wrapped it in numerous layers of heat shrink to make a grip. It’s just baaarely within the 0.1” envelope. The plug is a Stäubli (top quality Swiss brand) stackable plug. The wire is French-made 24AWG test lead wire from Cal-Test, but honestly I don’t like the wire: it “takes a set” too much, so it’s always creased, and the surface is super rubbery (not slick like good test lead silicone). I don’t use those much, either, because of the insertion force required.

Next are two bundles of jumper wires made with delightful 24AWG silicone wire from China (from a specific supplier, they’re not all this nice). The male pins are good quality Chinese “DuPont” contacts, but the female ones are made with genuine ultra-high-force Mini-PV contacts from Amphenol. Chinese DuPont female contacts are looser to begin with and loosen a lot more after a few insertions, whereas the genuine Mini-PV are specified at 1000 cycles, and the ultra-high-force versions are expressly designed for use as single connectors. Despite the Mini-PV contacts costing upwards of 10x as much as Chinese contacts, their vastly longer longevity and the aggravation they prevent makes them well worth it.

The thinner red jumper on its own is one made with 28AWG Chinese silicone. Absolutely lovely for breadboard use.

Last but not least, I’d be remiss if I didn’t mention that Pomona sells its model 4691 banana to pin adapters. They come in a few sizes, the smallest being this, the 0.8mm. They have rounded points (more or less hemispherical), and they’re significantly tougher to insert than the aforementioned torpedo-shaped HD pins. The 4691’s shaft is bendy, so you don’t have to have your fat banana cable’s weight dangling from the breadboard. But honestly, I never use them.

I much prefer my homemade leads made with Chinese silicone with crimped male DuPont pins on one end and a soldered Stäubli or Hirschmann banana plug (for permanent installation) or a screw-mount Pomona 1825 or spring-loaded WAGO 215 banana plug (for temporary cables) on the other end.

I’ve also experimented with making jumpers with TE MQS contacts. The housings are 0.1” pitch multi-pin automotive monsters, but using heat shrink does work. The pins are 0.025” square just like DuPont. As automotive connectors, they’re very robust: the male contacts are actually a solid pin (like a PCB header) welded onto the crimp terminal. The female ones are luxurious to insert onto a pin. The downside is that they’re a bit fatter than DuPont contacts, so by the time you’ve put heat shrink onto them, you’re just a bit above 0.1”, so you can’t line them up on adjacent rows. 2 or 3 will work, but beyond that it gets tight real fast.


I just tested the Test Leads, and they seem to both fit in the holes next to one another (it’s a snug fit). The molded strain relief is flexible, which helps out a lot.
The real problem begins when you need more than 2, or when other components or plugs are adjacent. (It’s not uncommon for me to have 4 or more DuPont pin cables going off the breadboard: 2 or 3 for power supply, then 2 for a voltage or current measurement, sometimes more to a second or third meter.) DuPont pins in DuPont housings are designed to fit within the 0.1” pitch and can be lined up in any number.

As you can probably tell, I’m quite the connector junkie, and put a lot of thought and care into my test leads, so I absolutely understand your motivation for wanting to make these leads. But I do think a bit more thought needs to go into the design, because I don’t feel your design quite yells “I really understand the use cases and constraints”.
« Last Edit: June 30, 2022, 12:03:09 am by tooki »
 
The following users thanked this post: ajb, eugene, Anders Petersson, cortes, Pitron

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #12 on: June 30, 2022, 12:47:06 am »
Hey Tooki,

Thank you for taking the time to write down all this information. I appreciate constructive criticism.

I’m going to have to read over your post a couple of time to take it all in.

I am working on a new design for the test leads and I’m definitely going to use all your feedback in this revision.

Thanks again
 
The following users thanked this post: tooki

Offline Berni

  • Super Contributor
  • ***
  • Posts: 4294
  • Country: si
Re: Breadboard Test Leads
« Reply #13 on: June 30, 2022, 05:28:17 am »
Yep i agree with others, this is way too bulky on the probe end.

You simply want a normal 1 pin header soldered onto the end of a thin wire and covered with heatshrink. That way the connector does not stick out a long way (potential for being snagged and bent) while the heatshrink lets it gradually bend coming out of it, providing strain relief to the wire so that it does not break under repeated bending.

I was actually considering making oscilloscope probes in this style (along with the option of plugging a micrograbber on the end) but those are a lot more complicated to make for a 10x probe that is properly compensated and works into the MHz
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 11537
Re: Breadboard Test Leads
« Reply #14 on: June 30, 2022, 07:03:21 am »
Yes.  That's exactly how I built the probe to pin lead extensions I posted back in 2020, which I have been using for a decade or so:

The clip adapters should have been built the same way - with a short flexible lead between the socket for the ordinary meter probe and the clip.

 

Online tooki

  • Super Contributor
  • ***
  • Posts: 8626
  • Country: ch
Re: Breadboard Test Leads
« Reply #15 on: June 30, 2022, 10:57:38 am »
It’s funny how different people’s taste in test leads is. I know adapters that slip onto probe tips are very popular, so people must like them. Me, I hate that, I don’t want anything on my probe, I want a dedicated lead. I’m sure others hate having a bunch of different leads taking up space. I guess that’s why the market has them all. :)
 
The following users thanked this post: ajb, mindcrime

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #16 on: June 30, 2022, 09:39:41 pm »
Thanks for all the feedback.

I’ve been speaking to my manufacturer today and I would like to give everyone an update on the progress.

We’ve been working on sourcing new components for the Rev2 breadboard test leads. We were able to find square 0.5mm x 0.5mm tampered steel needles, to use as the heads. Does anyone have a preference between square or rounded heads?

We are going to completely redesign the molded strain relief for the needle heads. The new design is going to be minimalist and discreet. This design is going to be similar in appearance to the net tail of apple’s charging cable. (I attached a picture for reference.)  The molded strain relief is going to be made out of TPE (a soft elastic material). We are still working on the design and dimensions; I will post a picture of it in a future update.

The wire is going to be 1 meter long and the insulation material will be silicone.  The wire gauge will be 24AWG. Hopefully, we will be able to find some wire with around 40 strands.

We are also looking for a new banana plug with a low contact resistance.

I am not an expert in cable designs. However, this is a project I’ve been wanting to do for several years.  :)

Thanks again for all the feedback. I plan to keep all of you updated on the new design.
« Last Edit: June 30, 2022, 09:43:06 pm by Pitron »
 

Online tooki

  • Super Contributor
  • ***
  • Posts: 8626
  • Country: ch
Re: Breadboard Test Leads
« Reply #17 on: June 30, 2022, 10:18:08 pm »
Thanks for all the feedback.

I’ve been speaking to my manufacturer today and I would like to give everyone an update on the progress.

We’ve been working on sourcing new components for the Rev2 breadboard test leads. We were able to find square 0.5mm x 0.5mm tampered steel needles, to use as the heads. Does anyone have a preference between square or rounded heads?

We are going to completely redesign the molded strain relief for the needle heads. The new design is going to be minimalist and discreet. This design is going to be similar in appearance to the net tail of apple’s charging cable. (I attached a picture for reference.)  The molded strain relief is going to be made out of TPE (a soft elastic material). We are still working on the design and dimensions; I will post a picture of it in a future update.

The wire is going to be 1 meter long and the insulation material will be silicone.  The wire gauge will be 24AWG. Hopefully, we will be able to find some wire with around 40 strands.

We are also looking for a new banana plug with a low contact resistance.

I am not an expert in cable designs. However, this is a project I’ve been wanting to do for several years.  :)

Thanks again for all the feedback. I plan to keep all of you updated on the new design.
Because of the shape of breadboard contacts, I’d recommend round. But either would be absolutely fine, provided it’s got a tapered point.

FWIW, this is the wire that I like: https://www.aliexpress.com/item/32788107178.html

That’s the 24AWG, but they have every size. See the attached stranding and dimensions table. The only bad thing I have to say about them is that they do not have a true purple; their “purple” is maroon-ish brown. In my picture above, the “purple” is the one in the center, next to blue and gray, the one whose plug has a strong reflection on it.
« Last Edit: June 30, 2022, 10:25:16 pm by tooki »
 
The following users thanked this post: Anders Petersson, Pitron

Offline Doctorandus_P

  • Super Contributor
  • ***
  • Posts: 2311
  • Country: nl
Re: Breadboard Test Leads
« Reply #18 on: June 30, 2022, 10:37:14 pm »
Already quite a long time ago I made my own.

I made them from hardened steel sowing needles. (They are cheap and you can buy them in all kind of lengths and thicknesses). On the back side I soldered a single contact broken off from a single row (high quality) 2.54 pitch header. Then I put some hot glue on the needle and added shrink tube, and repeated that for a total of 3 layers to give the probe some thickness. Because it has no wire dangling from the back end, they can't get entangled either and you can stow a few of them in a small area box or drawer. The female plug at the back end accepts regular "dupont" wires which you have of course always available when working with breadboards.

Even if your probes are made from good quality supple wire with silicone isolation they are still much too thick and heavy to work with breadboards.

I also never iked any of the normal DMM probes. I made my own from simple "loudspeaker cable". On one side I split the two wires apart for about 5cm and added 4mm banana jacks. On the other side I split the wires apart for about 20cm and I added 2mm Hirschman banana jacks, but I drilled a concentric hole in them of about 0.8mm thick and (again) soldered tips of sowing needles in them. The 12+cm handles of normal probes are much too big to work with almost any electronic circuits, and the 3cm long 2mm banana plugs work quite nice. The 2mm barrel of course also accepts the 2mm crocodile clamps.

I have also cut a section out of an inner bicycle tube and I put that on the under side of my DMM between the meter itself and it's rubber holster, so it's a loose hanging flap, and I put the crocodile clamps on them when I don't need them.
« Last Edit: June 30, 2022, 10:51:53 pm by Doctorandus_P »
 

Offline sleemanj

  • Super Contributor
  • ***
  • Posts: 2919
  • Country: nz
  • Professional tightwad.
    • The electronics hobby components I sell.
Re: Breadboard Test Leads
« Reply #19 on: July 01, 2022, 12:22:53 am »
This could be a Dragon's Den "I've sunk my life savings into this bad idea" moment.  Don't fall into the trap of losing sight of what is useful and desirable instead of just a fun challenge to get fabricated.

Simple flying leads to standard crimped dupont connector with an inline banana socket or plug is better in all regards, cheaper, more convenient, more versatile... sure it's not a "sexy molded silicone test lead" but it doesn't have to be.

Anyway, if you persist with the idea, I would suggest making them right-angle so the probes lie-flat, having the probes sticking up in the air like that is just awkward, a disaster waiting to happen.
~~~
EEVBlog Members - get yourself 10% discount off all my electronic components for sale just use the Buy Direct links and use Coupon Code "eevblog" during checkout.  Shipping from New Zealand, international orders welcome :-)
 
The following users thanked this post: Pitron

Offline rcjoy

  • Contributor
  • Posts: 17
  • Country: us
Re: Breadboard Test Leads
« Reply #20 on: July 01, 2022, 02:38:44 am »
I use these banana-to-pin adapters from Pomona, part #4691:

https://www.digikey.com/en/products/detail/pomona-electronics/4691-2/736931

The ends are actually flexible, and work quite well.

 

Online tooki

  • Super Contributor
  • ***
  • Posts: 8626
  • Country: ch
Re: Breadboard Test Leads
« Reply #21 on: July 01, 2022, 05:15:47 am »
I described (and showed a photo of) those a day ago. ;)
 

Offline bd139

  • Super Contributor
  • ***
  • Posts: 22932
  • Country: gb
Re: Breadboard Test Leads
« Reply #22 on: July 01, 2022, 05:54:23 am »
I just use a cut off leg from a resistor poked into two holes to make a loop. Then connect that to Pomona minigrabbers  :-//

Advantage being you can use the same methodology for dead bug prototypes.
 

Offline Pitron

  • Contributor
  • Posts: 33
  • Country: us
    • Pitron Project Website
Re: Breadboard Test Leads
« Reply #23 on: July 01, 2022, 10:03:14 pm »
Thanks again for all the feedback.

I think one of the drawbacks of the original design is the price. It seems most people would rather use cheap mini grabbers, alligator cable or build the cable themselves than to pay $18 for a cable specially made for breadboarding. Because of this, I am going to aim for a price of $9 USD for Rev2. I would appreciate some feedback on this.

I attached a picture of the current design for the molded strain relief (grip). This is my first attempt at the design of Rev2, so the dimensions and overall layout can still be changed.

I am still looking for 0.5mm rounded tampered steel pins. If I can’t find any, I’ll stick with the 0.5mm x 0.5mm square steel pins.

The wire we found is 24AWG and has exactly 40 strands.

The manufacture told me that the banana plugs I’m currently using is made from copper and has a low contact resistance. I’m going to take apart some the cables to do some additional testing. I’ll post the results in another update.

Thanks again everyone.

 

Offline bd139

  • Super Contributor
  • ***
  • Posts: 22932
  • Country: gb
Re: Breadboard Test Leads
« Reply #24 on: July 01, 2022, 10:07:53 pm »
I would rather use expensive mini grabbers.

The problem with this approach is that the cables and the connectors are huge compared to the breadboard pin. That means you effectively are putting a lot of leverage on breadboard headers and are likely to damage them or snap the pin off the connector. I know because I did that a couple of times.

You can see roughly what I do here. I use the binding posts on the board for power and clip anything else on component leads



But I don't even do that now. It's all FR4 sheets because the infernal breadboards are so unreliable, particularly after you've poked leads into them.

 
The following users thanked this post: Pitron


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf