[OldSalt1945]

I ordered one of James Newton's THB6064AH Stepper Motor Driver by MassMind.org.
I am hoping it will solve a problem I'm having with my stepper motors.
This post is to document my progress and to, hopefully, gain some advice from other members.

I built a Sidewinder CNC. Lots of battles, things learned, things re-learned. I've been fooling around with this thing since last summer and still haven't gotten it to work reliably. I'm retired & cheap, so I tried to go the cheapest route and have paid twice for a lot of it.

Other than mine, I have never seen a CNC Router in person, so all suggestions are welcome.

My current problem is the Z-axis which loses steps when moving up or down. This is random and whether it loses them on the up or down stroke depends on how many mini-bungie cords I use to offset the Z-axis weight. 7 is not enough, 8 is too much. With no bungies, it bores a hole through the basement floor. I have a spare motor, so swapped that in. No luck. I switched the X and Z drivers. No change. X and Y-A seem to work OK. I also switched the motors from the X and Z axes. Again a swing and a miss.

I can easily turn (when it's not moving) or stop (when it is moving) any of the motors by grabbing the 3 inch handwheel on the back of each motor. It takes only light fingertip pressure. No pipe wrench required.

I'm getting tired of turning walnut into kindling, so I need help.

CURRENT SETUP:
Universal Gcode Sender
Arduino UNO running GRBL .9i
CNC Shield (generic Chinese 4-axis)
Pololou 8825 drivers set to the maximum of 1.5 amps; set to single-step
Nema 23 Hybrid Stepper Motors: wired Bipolar Serial, 400 oz-in, rated current 2.83, resistance 1.6, VDC 4.52, inductance 7.2 mH
Dual motors on the Y-axis. Singles on X and Z.
24 volt 20 amp DMiotech Chinese power supply adjusted up to 30 volts
4-start 8 tpi leadscrews; no backlash; very little, if any, turning resistance. This gives 1/2" travel per revolution. It goes like a scalded dog when the step rate is cranked up, 7000 mm/min, but I found that to be a bit scary and fearing unreliability, backed it down; way down for Z.

GRBL settings are:
$0=10 (step pulse, usec)
$1=255 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=4 (dir port invert mask:00000100)
$4=0 (step enable invert, bool)
$5=0 (limit pins invert, bool)
$6=0 (probe pin invert, bool)
$10=3 (status report mask:00000011)
$11=0.008 (junction deviation, mm)
$12=0.002 (arc tolerance, mm)
$13=1 (report inches, bool)
$20=0 (soft limits, bool)
$21=1 (hard limits, bool)
$22=1 (homing cycle, bool)
$23=3 (homing dir invert mask:00000011)
$24=50.000 (homing feed, mm/min)
$25=1500.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=1.000 (homing pull-off, mm)
$100=15.800 (x, step/mm)
$101=15.800 (y, step/mm)
$102=15.800 (z, step/mm)
$110=5500.000 (x max rate, mm/min)
$111=4000.000 (y max rate, mm/min)
$112=1500.000 (z max rate, mm/min)
$120=500.000 (x accel, mm/sec^2)
$121=500.000 (y accel, mm/sec^2)
$122=200.000 (z accel, mm/sec^2)
$130=790.000 (x max travel, mm)
$131=790.000 (y max travel, mm)
$132=100.000 (z max travel, mm)

I have a couple of Arduino Mega's so could switch to that if someone thinks it will help. I don't want to have to buy Mach 3 and a desktop to run it. V-Carve Desktop software is gonna be a big enough bite when I get a machine good enough to warrant it.

I got inspired by James Newton's articles and videos concerning his THB6064AH driver board and ordered one to try out on the Z. If it works as described, I will order 3 more.

I will document my progress here.

His board costs a few bucks more than the Chinese boards, but I am tired of fighting the IFFY Chinese quality (don't ask me about the 4 6560 boards in my junk box). I will try using the heatsinks from them with James's board. They were only $5 each, so not a total loss. Fortunately I discovered they were crap before investing any time in them.

If anyone has advice on this or anything else you may notice in my setup, it will be welcomed.

If you guys can help this old fart get his CNC router working reliably, I might be persuaded to show you how to make 4-start Acme no backlash nuts with very little drag from bucket lids while only slightly irritating your wife. Awww hell, I'll do it anyway.

John

[awerby]

I've never heard of using bungee cords to offset a spindle's weight, and it doesn't sound like a good idea. Cords like that - or any tension spring - won't offset weight evenly; it's not enough to start with, and too much at the extremes of tension. I've tried constant-force springs, which worked as long as they lasted, but that wasn't very long. What worked best for me was gas struts, which exert a more linear force no matter where in the stroke they are. Another solution I've heard people use (but haven't tried myself) is a counterweight, which is less convenient to rig but also linear.

Those motors you're using have very high inductance, which means that they need a lot of power supplied to work efficiently. The formula 32 * (sq.rt.of) inductance = optimum max power input says those motors want about 86 volts to run at their best; at 30v it's not surprising they're faltering and easily stopped by hand. The fact that you're only giving them about half the current they want (1.5 amps vs. 2.83) isn't helping either.

If you want to keep using those motors, throw out all that arduino grbl junk and the Pololou drivers (or keep them for building a 3D printer, using much smaller motors) and buy 3 Gecko V203 drives http://www.geckodrive.com/g203v.html which can handle 80v and more current than you need. Get a power supply that can put out 80v and enough current (I like these: PS-10N80 - 1000W 80V Power Supply - AnTek Products Corp ) and that machine of yours will fly. Yes, it will cost some money, but isn't all that walnut starting to add up - not to mention the time you're spending tearing your hair out?

If you want to use James Newton's THB6064 drives, get some motors with less inductance that will work best at 50v or so and a power supply to match. Mach3 is totally worth the money, but if you can't spend it, go with LinuxCNC, which is free.

[James Newton]

Just to be clear... John doesn't yet have the THB6064AH drivers.. he is NOT having these problems with a MassMind.org THB6064AH driver, despite the title of the post. His /trying/ the MassMind driver to /solve/ the problems described in the post.

I totally agree with awerby that a geckodrive would be better... there is nothing that a geckodrive is NOT better than, so that's an easy statement. At more than twice the price, on a retiree's income, however... Are they really necessary?

Yes, high inductance motors move /faster/ with higher voltage, but faster is not Johns problem... loosing steps even at low speed in the direction of the Z axis "weight" (negative weight when using a stronger bungee) is the problem and that is cause by lack of current, as much as a lack of voltage. Voltage = speed, power = voltage * current. 1.5 amps at 30 volts is only 45 watts. With the MassMind THB6064AH driver he will have 2.83 amps at 30 volts or nearly 85 watts... close to double... and honestly, he's going to overdrive those motors and put heatsinks on them so he is really going to get more like 100 watts.

He is going to be just fine. And at half the cost, given some time soldering.

There is also absolutely nothing wrong with grbl.. I really think there is a HUGE advantage in NOT having the PC produce the step pulses. Windows is NOT a real time operating system, it's NOT designed for precise generation of timing signals. I can't prove it, but I'm pretty sure that a lot of random unexplained problems are caused by Windows deciding to take a rest in the middle of Mach 3 trying to produce a consistent pulse stream (cue the flame wars) And Pronterface or whatever user interface you want to use with grbl works just fine.

And there is certainly nothing wrong with using a bungee to offset gravity. That's what bungees were made for... basically... a weight hanging from a pulley would be better for long throws on the Z axis, but usually the Z axis isn't making really long runs. A few inches is usually all it needs, and a bungee to the ceiling is pretty consistent over that range. A spring might last longer...

I see this issue with the Z axis quite often, and I've solved it for people MANY times by just adding a spring or a weight hanging from a pulley.

There is a range from "too cheap to work" up to "too expensive to try" and there is a middle point where you don't break the bank and you still get "good enough" done. That's what we are going to hit.

[OldSalt1945]

JAMES IS CORRECT!!!!!!!!!!!!!!!!! I HAVE ORDERED HIS DRIVER BOARD TO SOLVE THE PROBLEM that I have using the Pololu drivers!!!!!!!!!!!!
I have not yet received it. I trust it will put me in tall cotton with bluebirds circling my grey head.

buy 3 Gecko V203 drives http://www.geckodrive.com/g203v.html which can handle 80v and more current than you need. Get a power supply that can put out 80v and enough current (I like these: PS-10N80 - 1000W 80V Power Supply - AnTek Products Corp ) and that machine of yours will fly. Yes, it will cost some money, but isn't all that walnut starting to add up - not to mention the time you're spending tearing your hair out?

Thanks for your advice, but a $750 (yikes) solution, for me, is no solution at all. That is not even a remote possibility.

I'm retired. I got nothing but time. Well, dependent on the Grim Reaper, of course.

John

[OldSalt1945]

"I've never heard of using bungee cords to offset a spindle's weight" ----- that's because I'm an innovator. And cheap. Didn't understand the spring specifications at McMaster Carr and didn't want to wait. I went to Menards and bought a box of 20 little bungee cords for $4. I disconnected the Z-axis from the stepper and let it down onto a postal scale - it weighed 14 lbs. I played around with testing combinations of the bungees until I determined the best combination of lift over stretching range (my Z-axis range is only 4 inches). I determined the best pre-load to make the lift force as much the same at the top of the range as at the bottom. I then attached of the little guys to the machine and tested it out with hand pressure. It turned out that 7 of them seemed about right. The Z settled in at about halfway between top and bottom of range and it didn't take much pressure to move it all the way up or down.

I didn't think about a weight hanging from a pulley mounted on the ceiling of the workshop. That would make the Z-axis pretty much weightless.

But it is all moot now. James's driver will let me get rid of the bungees and maybe even let the cat go for a ride on the "Z" train.

Although, I might just keep a couple of them just for conversation's sake. The bungees, not the cat. Well, OK, the cat too.

John

[OldSalt1945]

I measured the dead stopped holding torque of my motors in hopes that someone that is in the know will gain some insight and maybe keep me from further difficulties.

Note that the current drivers are the rather wimpy 8825 Pololu boards set to 1.5 amps (as high as they go).

My motor holding torque:
Power off = .15# @ 10"
Power on = .90# @ 10"

Tried a different motor rated at 3.5amps and got .70 @ 10" with power on.

10"-pound of torque = 10 x 16 = 160

.90# x 160 = 144 in-oz
.15# x 160 = 24
.70# x 160 = 112

Measuring this was relatively easy. I cut a stick 22" long. Marked the center. Drilled a hole 10" from the center and put a screw in the hole so that it protruded an inch or so.

I arranged the stick with the protruding screw pointing down while centering the center mark of the stick with the center of the motor shaft and clamped it to the hand wheel (could have been a pulley).

I powered up the controller and pressed a postal scale up against the screw and got the weight. The screw ensured that the reading was taken at exactly 10" from the center of the shaft.

[OldSalt1945]

What size wiring should I be using to go from driver to stepper. I am currently using a mix of 16 ga. and 18 ga. Judging by the size of the wires coming out of the steppers, I might be engaging in swatting a fly with a sledge hammer.

I have 3 heat sinks from defunct PC's. They measure 4" x 4" x 2" with many, many fins and have fans attached. I am thinking of attaching a piece of 1/8" x 3" x 12" aluminum to the heat sinks and then attaching the THB6064AH driver chips to the other side of the aluminum plate - with heat sink paste, of course. Is this about right or more overkill?

John

[James Newton]

I will now be demanding a picture of your cat riding the Z axis up and down. ,o)

PC heatsinks are great! You might not even need to power the fans, but having that option is always good. I would (personally) directly attach the drivers to the heatsinks, and then mount the edge of the heatsink to the aluminium plate, but the other way will very probably work just fine as well. Yes, paste is critical.

Sorry about the slow shipping on this order, by the way... I screwed up Friday and didn't get the packages out in time for the mail carrier, then Saturday they didn't pick up for some reason. I WILL go out today come hell or high water. And by hell I mean "I'll put them out now" and by high water I mean "I'll take them to the post office if they aren't picked up".

[OldSalt1945]

So, can anyone recommend the proper wire size for connecting the driver to the stepper? It is about 8' maximum run. I am currently using coat hanger wire wrapped with duct tape.

John

[OldSalt1945]

Next question.

Here are the specs for my motors.

Nema 23 Hybrid Stepper Motor Dual Shaft
Step angle 1.8 degrees
Positional accuracy +/- 5%
Number of Phases 2
Temperature 80 C Max
Rotor Inertia 530 gcm2
Weight 1.13 Kg

Note: the following was supposed to be in table form, but all the spacing was removed, leaving it a jumbled mess. Dot's the way you fix it.

Connection ....... Holding Torque ....... Rated................ Phase Resistance ....... Voltage................. Phase Inductance
..........................2 phases on........... Current/Phase.... Ohms +/- 10% .............Current/Phase......... (mH) +/- 20% (1 KHz)
..........................N.m/oz-in ...............Amps DC................................................ V DC ....................Typical

Unipolar ............. 2.0/283 ...................4.0 ......................0.8 .............................3.2 ..........................1.8

Bipolar(Serial) ..... 2.83/400................. 2.83.................... 1.6............................. 4.52 ........................ 7.2

Bipolar(Parallel) ... 2.83/400 ............... 5.66 .................... 0.4 ............................ 2.26 ........................ 1.8


Given this, wouldn't it be better to wire it Bipolar(Parallel) for the THB6064 drivers rather than Bipolar(Serial) as Pololu recommended for their 1.5 amp drivers?

John

[James Newton]

So, can anyone recommend the proper wire size for connecting the driver to the stepper? It is about 8' maximum run. I am currently using coat hanger wire wrapped with duct tape.

John

"coat hanger wire wrapped with duct tape." LOL... now THAT is neat! I've never heard that one before... I have no idea how conductive coat hanger wire is... And BTW multi-meters can't measure below a few ohms accurately. Takes a special tool. I would ASS-U-ME that your setup is fine, but it's never been done that I've heard of in years of doing this, so I don't really know.

I use speaker wire, or (free) old outdoor extension cords: 3 conductors per cord, so 3 axis times 4 wires = 12 divided by 3 means 4 cords, but at the end you have to strip back a lot of the outside covering for the distance between motors. It's not so bad if you run whichever motor is connected to your base on the 3rd wire in each cord, then run two with the remaining 2 over to one axis and the other two with 2 to the last axis. Wow... that made no sense, did it?

In any case, long runs of high power high frequency signals are a bad idea. Make the drivers as close as you can while still keeping the step and direction cables as short as possible.

[James Newton]

Yes. Bipolar parallel should work better. Here is a good chart and description of the advantages / disadvantages.

techref.massmind.org/Techref/io/stepper/connections.htm

[jfong]

Found this post from Mariss owner/designer of Geckodrive regarding using 22gauge wire. I use 20gauge since I bought a big roll years ago.

"Most will agree 22-gage wire is pretty small (0.64mm or 0.025" diameter). Let's see how it would work out wiring to a 7A per phase motor 10' (3m) away.

22-gage wire has 0.16 Ohms resistance for a 10' length. Two wires are needed per coil so that's 0.32 Ohms. The voltage drop will be 2.2V due to wire resistance at 7A. If your power supply voltage was 65VDC then it just became a 63VDC supply as far as the motor is concerned. Will your motor know the difference? Not at all; it draws 7A at low speed where supply voltage doesn't matter.

At high speed your motor phase current drops to 3A. The cable drop becomes 1V, the supply becomes 64VDC instead of 65VDC. Does the motor care? Not at all again.

Will the cable melt? Cable dissipation is 72 times 0.32 or 15 Watts. That works out to about 1/8W per inch. It will be warm but not hot. At high speed it's 3W and 0.024W / inch. Not even warm.

Mariss"

[OldSalt1945]

Found this post from Mariss owner/designer of Geckodrive regarding using 22gauge wire. I use 20gauge since I bought a big roll years ago.

"Most will agree 22-gage wire is pretty small (0.64mm or 0.025" diameter). Let's see how it would work out wiring to a 7A per phase motor 10' (3m) away.

22-gage wire has 0.16 Ohms resistance for a 10' length. Two wires are needed per coil so that's 0.32 Ohms. The voltage drop will be 2.2V due to wire resistance at 7A. If your power supply voltage was 65VDC then it just became a 63VDC supply as far as the motor is concerned. Will your motor know the difference? Not at all; it draws 7A at low speed where supply voltage doesn't matter.

At high speed your motor phase current drops to 3A. The cable drop becomes 1V, the supply becomes 64VDC instead of 65VDC. Does the motor care? Not at all again.

Will the cable melt? Cable dissipation is 72 times 0.32 or 15 Watts. That works out to about 1/8W per inch. It will be warm but not hot. At high speed it's 3W and 0.024W / inch. Not even warm.

Mariss"

Excellent answer. Not only does it give me the answer, but it gives me some insight into why.
I am currently using speaker wire of 18ga, but will need to add some extensions to accommodate rearrangement to a permanent electronics box. Now I know what the minimum requirements are and why.

Thank you.

John

[OldSalt1945]

Yes. Bipolar parallel should work better. Here is a good chart and description of the advantages / disadvantages.

techref.massmind.org/Techref/io/stepper/connections.htm

Thank you.

I had read your techref, but being a neophyte, I wasn't certain I wasn't missing something.

John

[OldSalt1945]

I have no idea how conductive coat hanger wire is...

It is not the conductivity so much as the flexibility.

Takes a special tool.

No need to insult me.:nono:

I use speaker wire.

Actually, I am using speaker wire as well. Some is 18ga.; some is 16 ga. If I end up rewiring it, I will spring for 20ga. of the 4 proper colors; yellow, red, blue, orange to match the motors. I was mostly trying to make do with what I had until I determined if I would stay interested.

[jfong]

Mariss gave great answers. I have about a dozen gecko drives, servos and stepper. He even answered the support phone years ago and quickly solved my problem. Never have I had a problem with any of his drives in over 10 years since.

[OldSalt1945]

Well, James, you really know how to aggravate someone.

You should have known that I would find your THB6064AH driver to be most wondrous. And, knowing that, you should have sent me the other 3 drivers that you should have known I would need.

I just ordered them from you.

All I can say is WOW!!!!!!

I installed it on my Z-Axis because that's what I was having the most trouble with. I changed the wiring of the motor to be bipolar/parallel. I set the power supply to 35.6 volts (any higher would cook the remaining Pololu drivers). I did all the adjusting you outline in the instructions and started playing with it. Then I got curious and pressed down on the Z while sending an up command to GRBL from Universal Gcode Sender. No problem. I pressed harder. No problem. I put my postal scale on the router mount and did it again. I put 34 pounds of down force on the Z and it had no problem going up. If you recall, the lead screws are 4-start 8 tpi. 1 revolution = 1/2 inch travel. Get ready for the ride of your life kitty!

I found it smooth and quiet. I have it set for a hair under 4 amps. I used the suggested jumpers 2 and 3 for 40% decay and 16 microsteps.

I found the instructions adequate. They are not of the hand-holding variety, describing the placement of every component in detail. Since the board was designed with a bunch of optional things and future stuff accommodated, I found myself confused a few times, but worked through it. I'm not used to seeing a PCB with several missing components. The placement of the red "fault" LED was very confusing. A good closeup photo would be of immense help. I fooled around for at least a half hour ensuring that I got this right. I didn't want to let any magic smoke escape.

You really should consider making a high quality photo of a completed board showing the placement of all the components and including it in the instructions.

By the way, the PCB is of first rate quality.

I cleaned the PCB with alcohol to avoid the soldering difficulties you had in your assembly video. Before attaching the THB6064 IC, I put a light coating of solder resin on all the solder pads. This made the soldering go MUCH easier. If only you had made the board a 1/4" bigger so that the silkscreen could clearly show what the connectors and jumpers are. Documentation is never at hand when needed.

The PMinMO - Ramps adapter cable was VERY handy. I just popped out the Pololu driver and replaced it with the adapter and cable.
I was having some difficulty figuring out how to apply 5 v power to the driver board since the only provision for doing so is pin 9 of the PMinMO and it is covered up with the adapter cable. After chewing on it for a while, I noticed that the Pololu "Reset" pin is active low AND is tied to +5v. I checked with the multimeter and found it to be so. I then soldered a jumper wire from PMinMO pin 9 to Pololu "Reset". It works. You might consider running a optional line with solder pads in a manner similar to how you handle the "Enable" signal in a future version of the adapter.

When I get the other drivers for the X and Y-A axes, I will write a more complete review, giving feeds and speeds, etc. I just got it installed an hour ago. With the Z-axis, there isn't much you can do about testing speed and the like. It only goes 4 inches.

I would have no difficulty recommending this board to anyone who can solder competently and has some amateur understanding of electronics and knows how to use a multimeter.

In fact, I recommended it to one of my favorite people, me. That's why I ordered 3 more.

John

[James Newton]

Well, James, you really know how to aggravate someone.

You should have known that I would find your THB6064AH driver to be most wondrous. And, knowing that, you should have sent me the other 3 drivers that you should have known I would need.

I just ordered them from you.

There is this little matter of payment... When you order 1 you get 1 ,oP

LOL... Glad it worked for you, happy to sell you more.

All I can say is WOW!!!!!!

I installed it on my Z-Axis because that's what I was having the most trouble with. I changed the wiring of the motor to be bipolar/parallel. I set the power supply to 35.6 volts (any higher would cook the remaining Pololu drivers). I did all the adjusting you outline in the instructions and started playing with it. Then I got curious and pressed down on the Z while sending an up command to GRBL from Universal Gcode Sender. No problem. I pressed harder. No problem. I put my postal scale on the router mount and did it again. I put 34 pounds of down force on the Z and it had no problem going up. If you recall, the lead screws are 4-start 8 tpi. 1 revolution = 1/2 inch travel. Get ready for the ride of your life kitty!

That's what a good driver will do for you. Wait 'till you see what the X and Y axis will do for you.

I found the instructions adequate. They are not of the hand-holding variety, describing the placement of every component in detail. Since the board was designed with a bunch of optional things and future stuff accommodated, I found myself confused a few times, but worked through it. I'm not used to seeing a PCB with several missing components. The placement of the red "fault" LED was very confusing. A good closeup photo would be of immense help. I fooled around for at least a half hour ensuring that I got this right. I didn't want to let any magic smoke escape.

You really should consider making a high quality photo of a completed board showing the placement of all the components and including it in the instructions.

Well, there IS a picture just above the "Final Test..." section in the manual. It shows both version and the red LED. That might not be terribly visable in the printed copy that comes in the manual (yes, I send a paper manual with each kit) but it's very visible on the web page:
techref.massmind.org/techref/io/stepper/THB6064/index.htm
Here is an even higher res copy of it which you can get by clicking on that picture:
Attachment 319272

By the way, the PCB is of first rate quality.

I cleaned the PCB with alcohol to avoid the soldering difficulties you had in your assembly video. Before attaching the THB6064 IC, I put a light coating of solder resin on all the solder pads. This made the soldering go MUCH easier. If only you had made the board a 1/4" bigger so that the silkscreen could clearly show what the connectors and jumpers are. Documentation is never at hand when needed.

Yeah... no... you gotta read the docs. There is a step by step in there... Good job on the soldering! Resin makes all the difference.

The PMinMO - Ramps adapter cable was VERY handy. I just popped out the Pololu driver and replaced it with the adapter and cable.
I was having some difficulty figuring out how to apply 5 v power to the driver board since the only provision for doing so is pin 9 of the PMinMO and it is covered up with the adapter cable. After chewing on it for a while, I noticed that the Pololu "Reset" pin is active low AND is tied to +5v. I checked with the multimeter and found it to be so. I then soldered a jumper wire from PMinMO pin 9 to Pololu "Reset". It works. You might consider running a optional line with solder pads in a manner similar to how you handle the "Enable" signal in a future version of the adapter.

Ah... your Chinese Shield doesn't supply +5 to the Pololu's on their power pin? Wierd... On the RAMPS shield it's JP2, pin 2 which goes right to the VDD pin on the Pololu drivers. We connect that to our +5 via the PMinMO on pin 9.

When I get the other drivers for the X and Y-A axes, I will write a more complete review, giving feeds and speeds, etc. I just got it installed an hour ago. With the Z-axis, there isn't much you can do about testing speed and the like. It only goes 4 inches.

I would have no difficulty recommending this board to anyone who can solder competently and has some amateur understanding of electronics and knows how to use a multimeter.

In fact, I recommended it to one of my favorite people, me. That's why I ordered 3 more.

John

Thanks for the recommendation, and I'll pack up your order ASAP.

[OldSalt1945]

Ah... your Chinese Shield doesn't supply +5 to the Pololu's on their power pin? Wierd... On the RAMPS shield it's JP2, pin 2 which goes right to the VDD pin on the Pololu drivers. We connect that to our +5 via the PMinMO on pin 9.

Rats! Troublemaker. Now I have to go re-inspect the Pololu adapter and see if I missed the VDD pin.
This sort of thing happens to people who think they know more than they actually do know.
Looks like I fixed something that wasn't broken.

UPDATE: I took my ill-advised jumper wire off the adapter and it still works just fine without it.

John