The question is:
On "step zero", What is the state of transitors?
How I can check?
The question is:
On "step zero", What is the state of transitors?
How I can check?
Power = 1/2 *L* I^2 gives the instantaneous energy stored in an inductor as the current ramps up to the set value. You are incorrectly assuming that this energy is discharged into the chip when the transistor turns off. The current only drops slightly during the PWM off time. It shows up as ripple on the waveform. The heat energy dissipated in the chip continues to be I^2 *R, even during a step cycle when the current changed direction.
It cannot be recycled. The current needs to flow through the mosfets or diodes. The loss can be reduced by using lower resistance fets.For all the above, I think that energy dissipated as extra heat can be recycled and stop damaging the ICs. What do you think?
Changing the order of the factors does not change the product.
So, what's the point?
So, you deny that there is a Back EMF?
And denies that the energy of this "spike" can be sent to another location for later use?
And you like, I have to prove that its possible?
I do not need to prove it to you.
All mosfets have intrinsic diodes.
riphet,
I suggest you read the following blog:
Slow, Mixed and Fast Decay Modes. Why Do We Need To Complicate Things? | EBLDC.COM
Which seems to be written for a high school class at the beginning, but getting into the technical later on. The blog's comments are also worth to read as they have some explanations for back EMF, body( parasitic, intrinsic) diodes, free wheeling diodes, and decay mode issues.
htrantx
I deny back EMF. Even Al Gore can't convince me.
You are right. Let's send it to the neighbor's house.And denies that the energy of this "spike" can be sent to another location for later use?
You most certainly do. It is the law.And you like, I have to prove that its possible?
I do not need to prove it to you.
Has anyone tried this driver yet?
I see they're back on ebay: TB6600 1 Axis Stepper Motor 2 Phase Drive Board for CNC Router Beter with TB6560 | eBay
And a better price and ~different board here: New Product 4.5A TB6600 stepper motor driver board-in Motor Driver from Industry & Business on Aliexpress.com
The first one appears to have cleaner soldering. The second has current sense points.
David Malicky
I made my own with the tb6600 chip sample I received from Toshiba. It works great. The chip will supposedly sell for about $2 in small quantities.
H500--Thanks for the info, good to hear it's working great.
David Malicky
An update -- I bought one each of the Haoyu (black pcb) and Rattm (red pcb) TB6600. I've done a little bench testing and so far, both work very well. Comparing the two, each has ads and disads.
The Haoyu seems better made:
- The Rattm had a 1mm pad between the chip and heatsink (presumably conductive, but why so thick?), which prevented the pcb from screwing down parallel to the heatsink. I replaced the pad with paste--easy enough.
- The Haoyu's screw terminals are nicer, pull-up, and are more secure. The Rattms are cheap but do the job. {EDIT: Not really. Its quick connect feature is flimsy enough that the motor connector pulled out slightly when I moved the drive about an inch. Of course, that fried the TB6600 and it took my power supply with it. If using the Rattm, I'd glue the connectors on permanently or replace them.}
The Rattm pcb lacks terminal markings for step and direction (there's white-out over old marks).
- {EDIT: my Rattm amp pot turns opposite of how it should and how it's marked on the pcb: Full clockwise is 0.5A, full CCW is 4.5A.}
The Rattm makes some motor hiss and whistle as Lucas predicted. The Haoyu is almost silent.
Haoyu's supply capacitor is 220uF; Rattm's is 470uF. I'll augment anyway, so not an issue for me.
Haoyu's heatsink is about 30% bigger, but it runs much {EDIT: not 'much'} hotter. At a ~3.5A pot setting, the Haoyu heats up pretty quick to a chip temp of about 160F, and the thermal protection shuts it down after about 5 minutes -- it needs a fan. At the same pot setting, the Rattm's smaller heatsink only gets to ~115F and that takes 20 minutes. Maybe Rattm is doing something clever to keep it cool, or maybe it's not really delivering the rated amps. I plan on retesting with a kill-a-watt. {EDIT: the kill-a-watt revealed the amp pot issue, above. With the Rattm amp pot set opposite to its marking, and probably at 3.5A also based on the current sense points, it also gets hot. But still not as hot as the Haoyu, and it didn't shut down from over temp.}
The max pps & RPM capability seem great but confusing. Here are my test conditions for both drives:
- No load (not realistic, but it's consistent for now!)
- Probotix Green Monster with a 1.5" steel sprocket for more inertia
- 24 V power supply (pretty low for that motor)
- 3.5 A pot setting
- 1/4 stepping
The Haoyu gets the motor to 3000 RPM (40,000 pps). Rattm, 1500 RPM. Lowering the pot setting to 2.0 A, the Rattm gets it to 3000+ RPM. (Of course, there's little torque above ~1000 RPM, so these results don't really matter to CNC.) I wonder if the Rattm has some kind of throttle that keeps it running cool at lower performance? Maybe some experts here know what's going on. {EDIT: with the Rattm amp pot corrected and set at a probable 3.5A, and a 38V supply, it got the motor to 4250 RPM -- actually limited by Mach3 / my computer.}
Mid-band resonance damping seems excellent for both. I've accelerated 0-700 and 0-1400 RPM at the lowest rate Mach3 allows, and never detected a problem. Jogging steady state, 0-1000 RPM at 5% intervals, sometimes there was a little vibration around 800 RPM, but even fine tuning the RPM didn't make it worse.
Overall, both seem great for the $. [EDIT: the Rattm needs some work, but appears to be correctable.] The Haoyu is better in most respects except that it needs a fan, and maybe a big fan at 4.5 A. I plan to do some motor dyno tests in the future, so may have another update then.
David Malicky
There are some major and strange differences between the two.
The TB6600 has only one signal wich can affect it's performance and explain some of these differences (noise and heat):
OSC, this defines the chop frequency. Can you see wich value is used on both of them or measure the frequency?
Overall performance can of course also be influenced by the quality of the components used and PCB layout.
The value of the supply cap is good, there's no need to increase it but it must be a low ESR type, ex: panasonic UFM.
The 1500 RPM @ 1/4 microstepping for the Rattm is poor, unacceptable for me.
Interesting comparison. I'm surprised at the difference. The chip does not have many settings to choose from.
The temperature depends on the current and the chopping frequency. If the board runs cools but lack performance, I would suspect that the current is lower than what it was set to. You can measure it by putting an ammeter in series with one of the coils. But NEVER disconnect the wires when the drive is powered or you will kill it.
By the way, the 6600 does not have midband resonance damping. A low power supply voltage can make it run smoother at the expense of performance. I run mine at 40v.
You might be able to make the other drive run cooler by lowering the chopper frequency. Toshiba's reference design use a 51k resistor on the OSC to give about 45khz. I changed mine to 100k to get about 22khz.
I also noticed that the Chinese designs always use diodes at the output to try to lower the chip temperature. If they screwed up and used slow recovery diodes, the chip might actually run hotter. I never use them.
Are both boards silent, or do they hiss?
Thanks lucas and H500 -- that's great info! On the temperature mystery, the kill-a-watt showed the Rattm amp pot turns opposite of how it should and is marked on the pcb. Full clockwise is min amps, full CCW is max amps. As you thought, H500. With the Rattm amp pot set opposite to its marking (guessing 3.5A) it also gets hot. But still not as hot as the Haoyu, and it didn't shut down from over temp. So there is probably still something else going on. I haven't yet measured the actual motor currents--I recall reading somewhere that amp meters aren't accurate on those... instantaneous vs average? I was thinking of adding a ~0.1 ohm resistor in series with the motor leads and then scope the V across the resistor?
With the Rattm amp pot set to a corrected guess of 3.5A, and a 38V supply, it got the motor to 4250 RPM -- actually limited by Mach3 / my computer.
Just as I was finishing up retesting the Rattm, I moved the drive about an inch and its flimsy quick-connect motor plug pulled out slightly. Of course, that fried the TB6600 and it took the (also cheap) power supply with it. $40 per inch. I'm guessing the $20 supply isn't worth trying to fix? I checked inside--nothing obvious, and the fuse was alive and well.
I've edited my post above the corrected info.
Lucas, on measuring the chop frequency, for both drives, a scopemeter shows a period at idle of about 23 uS, so about 45 kHz like mentioned for the ref design. While spinning, though, I can only see the stepping pulses, and can't get a steady trace for the 23 uS period. I can post pics of the traces if helpful. Is the low ESR cap mainly for long life, or are there other advantages too?
H500, right, I should have said midband resonance control or something like that. I read here: http://www.cnczone.com/forums/1044657-post11.html
that the mixed decay mode is somehow effective at controlling resonance, but I'm not sure how. With 38V power, I retested for resonances on the Rattm. It did make some more vibration around 720 RPM, but nothing severe.
The Rattm hisses and whistles at idle (or it did), though curiously not consistently. Sometime it hisses, other times completely silent. But definitely louder at 38V than 25V.
I'll have more results on the Haoyu after I find another power supply.
David Malicky
A regular ohm meter should work because the waveform is sinusoidal when the the motor is moving fast enough, but not so fast that inductance mess up the wave form. If you have a scope, measure the voltage across one of the current sensing resistors. I= V/R. Note that the board has idle current reduction. Measurements at standstill won't work.
Use an ohm meter to check the fuses of your dead system. If you're lucky, that's all it is. Otherwise, replace the tb6600. They cost about $10 on Ebay. They should cost $1 to $3 when they become widely available.
I don't think mix mode decay does anything to for mid band resonance. It simply provide a cleaner sine wave. Mid band comp involves introducing a phase lead to the stepping pulses.
The hiss on the Rattm board suggest to me that their board was very poorly designed. I would avoid it in the future. My test board is silent. I didn't even put much effort in the layout.
The motor current should always be set by measuring the VREF voltage while adjusting the pot, there should be testpoints and a formula on how to calculate Vref vs motor current. Guessing shouldn't be needed.
A low esr cap will perform better at these high switching frequencies and will also last longer. It's the same problem on switching power supplies, PC mainboards etc.. Do a search on bulged or leaking electrolytics, some brands are famous: when they fail replace the cap's by quality ones and everything is fine again.
Looks like both use the same oscillator frequency, just to be sure: can you check the resistor value connected to pin 23 of the chip? It will probably be 51K.
The THB6064 has the option of 4 decay modes, these settings don't influence directly the midband resonance but make it worse for some motors. Fast decay is best at faster speeds but some motors don't like it and vibrate more on the resonance speeds. With the THB6064 you have the option to select what's best for your motors and setup.
"$40 per inch"... a good one , there goes the profit of buying cheap...
A good stepper drive needs a good PCB design (as H500 said) and selection of quality components. This is what I did on the THB6064 design, no compromises: only the best and the result is there: not a single failure, smoke, bang whatever... only happy customers and silent motors.
Do you have a link to the Rattm? Can't find it.
H500 and Lucas, Thanks for the info! H500, yes, the Rattm seems to have a string of problems. My only concern on the Haoyu is the temperature; I wonder if the idle current reduction wasn't working on mine, since it overheated at idle. Is idle current reduction automatic in the TB6600, or configured by the board? I couldn't find anything in the preliminary TB6600HQ datasheet, or the newer summary for the TB6600HG. I look forward to them being ~$2.
Lucas, yes, the Rattm has test points, and I found the Vref formula in the HQ datasheet, but I didn't know what Rnf was or if that older formula was still accurate. On mine at idle, I recall that Vref ranged from 0.5 to 2.8V while turning the amp pot from min to max. Thanks for the google tip on bulging caps. I traced pin 23 on each to its resistor, and both were indeed about 51k.
Here's the link to the Rattm I bought (they're on holiday like the rest of China now): New Product 4.5A TB6600 stepper motor driver board-in Motor Driver from Industry & Business on Aliexpress.com
The TB6064 kits look interesting but I want a presoldered board, and the higher amps of the 6600 helps a bit. I'll be needing a bunch of drives, which is why I'm reviewing the options more carefully. And there's one more: High Efficiency CNC Router Mill Lathe 1AXIS TB6600HG Stepping Motor Driver Board | eBay
David Malicky
The TB6600 doesn't have automatic idle reduction, it's done by additional circuitry on the board wich also includes the run led. I think they use pin3 (torque input) for this.
It only works if the correct step polarity is selected, the run led should be off when idle. Do you remember if it was?
The current calculation is the same as for the THB, RNF = 3 x .680 ohm in parrallel = .227 ohm for the Haoyu.
Higher amps for the TB6600 is only 0.5A and it seems that the power stage of both chips is the same only the control section is different. I had the THB running at 5A without problems.
If idle current reduction was working, you would know, because the torque goes down to 30%. As Lucas mentioned, the chip itself does not have the timing circuit built in. It is done with extra circuit. I consider it to be an indispensable feature. On my mill, the motors barely get warm because the the typical duty cycle is quite low.
I doubt that the 6600 can actually handle more current than the 6064. Heat is the issue. The 6600 has a 5v regulator built in. This will create more heat, especially if the designer didn't pay enough attention to how much 5v current is used by the external circuits.