It did work as intended. Further verification of every scenario, especially the power loss and restart will still be tested again, but that part did work with the stepper connected instead of the inductor/resistor previously, so this should be the ticket. I’ll keep playing with it. For now, it can print with the brake system connected where before it had to be removed to use the printer.
Could we use a lower wattage resistor for the brake since it is a motor simulation? 10 W is a lot. the inductor is 0.25 W currently.
v3 prototype board with smaller wattage resistors is in progress to test the smaller watt option to save space. My resistor stash only has 10 ohm resistors. So putting a bunch in parallel gets both lower resistance and a higher watt rating, and it is going to have both motor coils shorted since this brake doesn’t actually stop anything. It just loudly slows down the descent. I’m curious what a double brake will do.
Working on durability testing the V2 board currently installed.
6 hours into a 12 hour print for new primo trucks… (the whole reason I built Ernest - the v4 mp3dp)
the problem was a broken wire on z2. Z2 is the front right z motor. The pin was on the new plug to the brake board… one of the reasons I dislike DuPont plugs or really crimped connections in general. Soldering is much better. Fixed the broken wire and opted for half the print at 6 hours and this is what was produced.
single coil of one motor connected to the braking circuit vs both coils of one motors routed through the short-circuit resistor and inductor circuit.
All tests to date have been only one motor coil from each motor.
Result:
One coil is a loud “bumping” noise as the motor spins through to the bottom. this is effective, but very noticeable.
Two coils when powered off produce a very quite descent that is much slower
NOTE: In no case of z-brakes does the bed actually hold position. The brakes only act to slow the descent to minimize crash damage.
Board with double coil brake on one motor shown below (modified v1 board). Each brake circuit is 5 resistors of 20 ohms in parallel (because this is what I had on hand) and one inductor in series and 2 jst-xh plugs for board signal in and motor out connections
I can’t wait to try it. I have a bunch of questions for you but I think I will ask them as I go. I assume a few will get answered when I get it wired up. Thank you for leading the way on this part.
I build really high reliability stuff for work. At the high end, crimped connectors are always more reliable.
But, to get there, requires special tooling and really good training and workmanship on the part of whoever builds the cables.
A really sage grey beard once told me “The most reliable connection is the one you can correctly build.”
So, it’s important to know where those limitations are.
I’m really curious about the failed contacts. Would you be willing to share pictures of the failed crimps along with what suppliers and parts you used for the connector, contacts, and crimp tooling?
Looks like an opportunity to learn here and that is the point. Thanks for your help.
I am using a JST-XH connector with a crimper, a set of wire cutters and a pair of wire strippers. With exception of the crimper that I paid a modest amount for (not the cheapest one out there), these are budget tools. I’ll detail how I do it. It may be a stripped end that is too long/short and maybe using the tool incorrectly or even the wrong tool. here goes:
wire prep. strip insulation off and trim wire back so that of the 2 crimp zones on the pin, the wire is in the small one and the insulation is in the big one. If the insulation is not crimped, then the wire will break or pull out.
prep pin. bend pin and remove it and hold it or simple move it 90 degrees so the crimper can fit around it without messing up the others around it
slide wire into position and crimp the small area first on the 2nd to largest crimp with the crimper facing so the folding parts of the pin are pushed together and then into the wire
use the end of the crimper as pliers and push the outer larger crimp walls together so they fit in the largest crimp region and crimp it just like the smaller section.
crimp the insulation on the next smaller size setting.
crimp the insulation on the one smaller than the last one and crimp the wire portion on this size too.
crimp insulation and wire so they are uniformly the same size at this 3rd to largest size.
insert pin into jst-xh plug.
When unplugging, try not to pull on wires, use the plastic to unseat and not pull wires from pins or break wires.
I’m probably not doing this as written exactly, so the above should be considered the goal. Most of the time It works out, but I think trimming the wire length and sizing it before the crimp is probably the most likely issue.
Can you show a couple of close-ups of the crimped contacts, and a finished connector?
I use a crimp tool that has two positions, placing the contact in the tool such that the contact is actually out of the far end of the tool. I click it one click to keep it in place, then insert the stripped wire so that the insulation is in the back (larger) teeth, and the stripped wire is in the inner (smaller) area.
The crimp tool then crimps both the electrical contact area and the insulation retention area in one squeeze of the tool.
If the crimp is good, you should be just able to see the stripped wire beyond the inner electrical crimp wings, and the insulation (and only the insulation) should be grabbed securely by the outer (larger) wings.
The retention tab should be not affected by the crimp action.
I’ll see if I can find a quick link to a site that shows this more clearly.
You can probably get acceptable results with multiple passes with a tool like you show, but I’ve never had much luck that way.
When inserted the retention clips should lock easily and not be deformed at all.
I have one of the locking crimpers, but the crimp area is too big and smashes everything including where the pin from the other connection is supposed to go, so I don’t use them anymore.
I’ve taken a few photos as requested:
initial crimp (zoom with mediocre lighting = weird looking stuff) but the crimp part looks curled like it should.
notice that the upper insulation crimp part is pretty wide still. it doesn’t fit in my crimper, so I bend that part in
bent in:
I think the crimpers I have are pretty good for dupont, but the wire insulation I’m using is too large. Wire size, crimper, and insulation thickness all need to be within an acceptable range for this to work reliably. I’m missing one or more of them. These connectors for me are usually 80%-90% good. the JST-PH ones that are just smaller than these that are used on the motors with the 6 pin connections that only use 4 pins: those are the hard ones to get right and I’ve broken probably 60% of those ones. Those are smaller pins and smaller connectors, so I have to use the smallest crimp location on my crimpers.
Well diagnosed, and good documentation of your process.
The insulation on that wire is too large for that contact, so you’re struggling because the crimp that provides strain relief into the insulation is being significantly deformed.
I also don’t see strands of wire slightly beyond the end of the electrical (smaller) crimp area.
A good crimp would have those strands just visible beyond the electrical part of the crimp but not protruding into the boxy end of the contact that mates with the other connector.
So, that means the stripped length that you started with was probably a slight bit too short.
I’d bet that a ratchet style dual crimper, using wire with an insulation jacket that fits the contacts properly, and a slightly longer stripped section of the wire would make a big difference in the results you’re seeing.
The good news is that you understand all of the elements of what needs to happen for the crimp.
I agree, having a tool with the correct jaws/dies for making the crimp is worth the investment even if you only make a few connectors. The payback is in not having intermittent or failed connections ruin jobs and drive you nuts troubleshooting.
could you recommend one. I’m ready to level up on that having had my share of broken wire wrecks: Use Z-Brakes! - #82 by niget2002 (see spaghetti post above).
I have used these on several hundred wires (I used to make the wires for the kit by hand), Amazon.com
It takes a bit to get it right, and you are kinda doing it blind but most of the time the crimps work out well. I would love to try a Authentic set to see if they are any better. They real ones are $150++
Sadly, the one I use I have no idea where to find. I snagged it a long time ago at an electronics store. They sold the crimper itself and all the jaws were separate. I was in college and had to keep going back to the store to get other jaws as I did different projects in school that needed different connectors.
I typically also apply a small amount of solder on the crimp that does not include the insulation. If done right, this seems to work well without melting the insulation back on the second crimp. But a properly done crimp with the right tool probably doesn’t need this. I do it as a precaution since I feel it adds a little extra strength.
I’ve seen folks do this, mainly when they have trouble with using the wrong crimp tool and not getting a good mechanical crimp. It can be a mild help if the tooling or workmanship is otherwise terrible.
That’s true. It isn’t needed.
Further, soldering the crimp actually makes it less reliable, and I’ll describe some of the reasons why.
You wick solder and flux into the stranded wire. The whole layout of the crimp assembly provides for electrical termination and mechanical strain relief of the wire/connector assembly. Wicked solder can end up beyond the part of the crimp that captures around the insulation and strain relieves the wire. If the wicked solder is beyond that point, then you’ve introduced a way to mechanically break wire strands more easily.
Wicked flux is nearly impossible to clean correctly, and this flux will be up in the stranded part under the insulation. It will corrode the wire strands up under the insulation. I’ve seen wire degrade rapidly and fail because of this. Some flux is worse than others- but this is usually always a result from soldering these crimp contacts. Flux also accumulates on the contacts where it mates to the other connector, and this again degrades the connection over time.
Often times solder will accumulate on the contact, and these little protrusions can pose problems for properly inserting/locking the contact or worse make it impossible to unlock the contact if you ever need to rework or modify the cable assembly.
Over temp can damage the insulation as you note, and can swell it - again making insertion/extraction more problematic.
