Author Archives: Ben

New high-gear ratio Micro Metal Gearmotors

via Pololu Blog

Our Micro Metal Gearmotors are now available with 380:1 gearboxes, offering a new high gear ratio option between our existing 298:1 and 1000:1 versions. Unlike the 1000:1 gearmotors, which uniquely require a longer, more expensive gearbox to achieve such a big reduction, the 380:1 gearboxes fit everything in the same volume as all our lower gear ratios, so they are the same price as those lower-ratio versions and they work with all our micro metal gearmotor brackets.

What really sets these new units apart from our other gear ratios are their stainless steel gearbox plates, which are more durable than the ubiquitous brass ones, especially in applications with non-negligible radial loads. They also look way cooler!

380:1 micro metal gearmotor with stainless steel gearbox plates.

Micro metal gearmotor with brass gearbox plates.

The main point of this higher gear ratio is not to deliver more total torque but rather to enable slower speeds and lower current draws than our lower gear ratios at the same loads. That said, the 380:1 gearbox can withstand higher torques than our lower gear ratios thanks to its use of progressively thicker gears toward the output. Both the 380:1 and 1000:1 gearboxes have a recommended instantaneous torque limit of 2.5 kg*cm, while the lower gear ratios have a recommended limit of 2.0 kg*cm (note: we strongly advise keeping applied loads well under these instantaneous limits).

These new gearboxes are available paired with each of our five motor winding options in compact single-shaft or encoder-friendly dual-shaft configurations, resulting in the ten new options shown as related products at the bottom of this post. These are just the latest example of our continued commitment to being the best source for this popular form factor of gearmotor. You might see similar-looking motors elsewhere, but no one comes close to our offering, from the quality of the gears to our exclusive long-life carbon brush options to the overall breadth of our selection (over 100 versions!), all in stock for shipment the day you order.

Rated
Voltage
Motor
Type
Stall
Current
No-Load
Current
No-Load Speed
(RPM)
Extrapolated
Stall Torque
Max Power
(W)


Single-Shaft
(Gearbox Only)


Dual-Shaft
(Gearbox & Motor)
(kg ⋅ cm) (oz ⋅ in)
12 V high-power,
carbon brushes
(HPCB)
0.75 A 0.06 A 6000 0.09 1.3 5:1 HPCB 12V 5:1 HPCB 12V dual-shaft
3000 0.17 2.4 1.5 10:1 HPCB 12V 10:1 HPCB 12V dual-shaft
1100 0.39 5.4 1.1 30:1 HPCB 12V 30:1 HPCB 12V dual-shaft
650 0.67 9.3 1.1 50:1 HPCB 12V 50:1 HPCB 12V dual-shaft
450 1.0 14 1.1 75:1 HPCB 12V 75:1 HPCB 12V dual-shaft
330 1.3 18 1.1 100:1 HPCB 12V 100:1 HPCB 12V dual-shaft
220 1.8 25 1.0 150:1 HPCB 12V 150:1 HPCB 12V dual-shaft
160 2.5 35 1.0 210:1 HPCB 12V 210:1 HPCB 12V dual-shaft
130 3.0 42 1.1 250:1 HPCB 12V 250:1 HPCB 12V dual-shaft
110 3.3 46 1.0 298:1 HPCB 12V 298:1 HPCB 12V dual-shaft
85 5.0 69 1.1 380:1 HPCB 12V 380:1 HPCB 12V dual-shaft
35 10 140 1000:1 HPCB 12V 1000:1 HPCB 12V dual-shaft
6 V high-power,
carbon brushes
(HPCB)
1.5 A 0.10 A 6000 0.09 1.3 5:1 HPCB 6V 5:1 HPCB 6V dual-shaft
3000 0.17 2.4 1.3 10:1 HPCB 6V 10:1 HPCB 6V dual-shaft
1100 0.45 6.2 1.2 30:1 HPCB 6V 30:1 HPCB 6V dual-shaft
650 0.74 10 1.2 50:1 HPCB 6V 50:1 HPCB 6V dual-shaft
430 1.1 15 1.3 75:1 HPCB 6V 75:1 HPCB 6V dual-shaft
330 1.6 22 1.3 100:1 HPCB 6V 100:1 HPCB 6V dual-shaft
220 2.0 28 1.1 150:1 HPCB 6V 150:1 HPCB 6V dual-shaft
160 2.8 39 1.1 210:1 HPCB 6V 210:1 HPCB 6V dual-shaft
130 3.2 44 1.1 250:1 HPCB 6V 250:1 HPCB 6V dual-shaft
110 3.4 47 1.0 298:1 HPCB 6V 298:1 HPCB 6V dual-shaft
85 5.0 69 1.1 380:1 HPCB 6V 380:1 HPCB 6V dual-shaft
33 11 150 1000:1 HPCB 6V 1000:1 HPCB 6V dual-shaft
6 V high-power
(HP)
1.6 A 0.07 A 6000 0.11 1.5 5:1 HP 6V 5:1 HP 6V dual-shaft
3000 0.22 3.0 1.6 10:1 HP 6V 10:1 HP 6V dual-shaft
1000 0.57 7.9 1.5 30:1 HP 6V 30:1 HP 6V dual-shaft
590 0.86 12 1.3 50:1 HP 6V 50:1 HP 6V dual-shaft
410 1.3 18 1.4 75:1 HP 6V 75:1 HP 6V dual-shaft
310 1.7 24 1.3 100:1 HP 6V 100:1 HP 6V dual-shaft
210 2.4 33 1.2 150:1 HP 6V 150:1 HP 6V dual-shaft
150 3.0 42 1.1 210:1 HP 6V 210:1 HP 6V dual-shaft
120 3.4 47 1.1 250:1 HP 6V 250:1 HP 6V dual-shaft
100 4.0 56 1.1 298:1 HP 6V 298:1 HP 6V dual-shaft
84 5.5 76 1.1 380:1 HP 6V 380:1 HP 6V dual-shaft
31 12 170 1000:1 HP 6V 1000:1 HP 6V dual-shaft
6 V medium-power
(MP)
0.67 A 0.04 A 4400 0.06 0.8 5:1 MP 6V 5:1 MP 6V dual-shaft
2200 0.11 1.5 10:1 MP 6V 10:1 MP 6V dual-shaft
720 0.33 4.6 0.57 30:1 MP 6V 30:1 MP 6V dual-shaft
420 0.54 7.5 0.55 50:1 MP 6V 50:1 MP 6V dual-shaft
290 0.78 11 0.54 75:1 MP 6V 75:1 MP 6V dual-shaft
220 0.94 13 0.50 100:1 MP 6V 100:1 MP 6V dual-shaft
150 1.3 18 0.48 150:1 MP 6V 150:1 MP 6V dual-shaft
100 1.7 24 0.46 210:1 MP 6V 210:1 MP 6V dual-shaft
88 2.2 31 0.48 250:1 MP 6V 250:1 MP 6V dual-shaft
73 2.4 33 0.44 298:1 MP 6V 298:1 MP 6V dual-shaft
57 3.6 50 0.53 380:1 MP 6V 380:1 MP 6V dual-shaft
22 6.5 90 1000:1 MP 6V 1000:1 MP 6V dual-shaft
6 V low-power
(LP)
0.36 A 0.02 A 2500 0.05 0.7 5:1 LP 6V 5:1 LP 6V dual-shaft
1300 0.10 1.4 10:1 LP 6V 10:1 LP 6V dual-shaft
450 0.29 4.0 0.31 30:1 LP 6V 30:1 LP 6V dual-shaft
270 0.44 6.1 0.29 50:1 LP 6V 50:1 LP 6V dual-shaft
180 0.64 8.9 0.29 75:1 LP 6V 75:1 LP 6V dual-shaft
130 0.74 10 0.25 100:1 LP 6V 100:1 LP 6V dual-shaft
90 1.1 15 0.25 150:1 LP 6V 150:1 LP 6V dual-shaft
65 1.6 22 0.25 210:1 LP 6V 210:1 LP 6V dual-shaft
54 1.7 24 0.23 250:1 LP 6V 250:1 LP 6V dual-shaft
45 2.0 28 0.22 298:1 LP 6V 298:1 LP 6V dual-shaft
36 2.9 40 0.27 380:1 LP 6V 380:1 LP 6V dual-shaft
13 5.5 76 1000:1 LP 6V 1000:1 LP 6V dual-shaft

New 5:1 Glideforce light-duty linear actuators

via Pololu Blog

We have filled out our line of 5:1 Glideforce Light-Duty Linear Actuators to include all of Concentric’s available lengths by adding 2″, 6″, 8″, and 10″ versions, with and without feedback, to our existing 4″ and 12″ options. The low gear ratio makes these our fastest (but weakest) linear actuators, capable of lifting up to a few dozen pounds at speeds up to 1.7″ per second (44 mm/s) at 12 V. For stronger but slower options, we have versions available with a 10:1 gear ratio or 20:1 gear ratio.

This brings our total selection of light-duty actuators to 36 options:

Actuator
Type
Max
Dynamic
Load
No-Load
Speed
@ 12 V
Max-Load
Speed
@ 12 V
Current
Draw
@ 12 V
Nominal
Stroke
Length
With
Feedback
Without
Feedback
Light-Duty
(LD) 5:1
15 kgf
[34 lbs]
4.4 cm/s
[1.7″/s]
3.6 cm/s
[1.4″/s]
1.2 A –
3.2 A
2″ LACT2P-12V-05 LACT2-12V-05
4″ LACT4P-12V-05 LACT4-12V-05
6″ LACT6P-12V-05 LACT6-12V-05
8″ LACT8P-12V-05 LACT8-12V-05
10″ LACT10P-12V-05 LACT10-12V-05
12″ LACT12P-12V-05 LACT12-12V-05
Light-Duty
(LD) 10:1
25 kgf
[55 lbs]
2.8 cm/s
[1.1″/s]
2.3 cm/s
[0.9″/s]
1.2 A –
3.2 A
2″ LACT2P-12V-10 LACT2-12V-10
4″ LACT4P-12V-10 LACT4-12V-10
6″ LACT6P-12V-10 LACT6-12V-10
8″ LACT8P-12V-10 LACT8-12V-10
10″ LACT10P-12V-10 LACT10-12V-10
12″ LACT12P-12V-10 LACT12-12V-10
Light-Duty
(LD) 20:1
50 kgf
[110 lbs]
1.5 cm/s
[0.57″/s]
1.2 cm/s
[0.48″/s]
1.2 A –
3.2 A
2″ LACT2P-12V-20 LACT2-12V-20
4″ LACT4P-12V-20 LACT4-12V-20
6″ LACT6P-12V-20 LACT6-12V-20
8″ LACT8P-12V-20 LACT8-12V-20
10″ LACT10P-12V-20 LACT10-12V-20
12″ LACT12P-12V-20 LACT12-12V-20

New products: ACS724 current sensor carriers

via Pololu Blog

We now have new current sensors based on Allegro’s ACS724, the successor to the ACS714 that we have been using for many years. The ACS724 offers a number of exciting improvements over the ACS714, including more current range options (up to ±50 A!), over twice the sensitivity for the ±5 A version, a higher bandwidth for faster response times, and differential Hall sensing for substantially reduced interference from ambient magnetic fields. In quick tests, we saw a variation of around 1% of the full range just from changing the orientation of the ACS714 in space (because of the Earth’s magnetic field), while the ACS724 output stayed steady regardless of orientation. We also tried bringing a small magnet close to each sensor, and its effect on the output was many times smaller on the ACS724.

These bidirectional and unidirectional current sensors are a simple way to gain fundamental insight into the performance of your system. You can use them for closed-loop torque control of actuators, tracking power consumption over time, or even as inexpensive current probes for an oscilloscope. They output an analog voltage that varies linearly with the current passing through them, and because they use the Hall effect to measure the current, they offer full electrical isolation of the current path from the sensor’s electronics. This method of sensing means the sensor can be inserted anywhere into the current path, including on the high side, and because their current path resistance is on the order of 1 mΩ or less, they have minimal effect on the rest of the system.

Five different current ranges are available:

Together with the Broadcom ACHS-712x current sensors we released last month, this brings our full current sensor lineup to thirteen sensors:


ACS709 Current
Sensor Carrier

ACS711EX Current
Sensor Carriers

ACS714 Current
Sensor Carriers

ACS724 Current
Sensor Carriers

ACHS-712x Current
Sensor Carriers
Sensor IC: ACS709 ACS711EX ACS714 ACS724 ACHS-712x
Current range / sensitivity(1): ±75 A / 28 mV/A ±15.5 A / 136 mV/A
±31 A / 68 mV/A
±5 A / 185 mV/A
±30 A / 66 mV/A
0–⁠10 A / 400 mv/A
0–⁠30 A / 133 mV/A
±5 A / 400 mV/A
±20 A / 100 mV/A
±50 A / 40 mV/A
±10 A / 185 mV/A
±20 A / 100 mV/A
±30 A / 66 mV/A
Path resistance: 1.1 mΩ 0.6 mΩ 1.2 mΩ 1.2 mΩ 0.7 mΩ
Bandwidth 120 kHz 100 kHz 80 kHz 120 kHz 80 kHz
Vcc range:(1) 3 V–5.5 V 3 V–5.5 V 4.5 V–5.5 V 4.5 V–5.5 V 4.5 V–5.5 V
Size: 0.82″ × 0.9″ 0.7″ × 0.8″ 0.7″ × 0.8″ 0.7″ × 0.8″ 0.7″ × 0.8″
Special features: configurable
over-current threshold,
low-voltage operation,
high bandwidth
over-current fault pin,
low-voltage operation
Differential Hall sensing
rejects common-mode fields,
high bandwidth
1-piece price: $9.95 $3.25 $9.95 $9.95 $4.95
1 Sensitivity based on when Vcc is 5V.

Introductory special

As usual, we are offering an extra introductory special discount on the ACS724 current sensor carriers, to help share in our celebration of releasing a new product. The first hundred customers to use coupon code ACS724INTRO can get up to five units for just $5.55 each!

New products: D36V28Fx Step-Down Voltage Regulators

via Pololu Blog

I am happy to announce the release of our newest regulators, the D36V28Fx family of step-down voltage regulators. These regulators support a wide input voltage range (up to 50 V!) and can deliver up to 4 A, making them well suited for use with power-hungry processors like the Raspberry Pi and projects involving servos or small motors.

Step-Down Voltage Regulator D36V28Fx, assembled on breadboard.

Step-Down Voltage Regulator D36V28Fx, bottom view with dimensions.

The family consists of six fixed output voltage versions between 3.3 V and 12 V:

And since we make these ourselves here in Las Vegas, we can also quickly make versions with custom output voltages; please contact us us for more information.

Comparison to the D24V22Fx step-down regulator family

Top view of D36V28Fx step-down voltage regulator.

Top view of D24V22Fx step-down voltage regulator.

The D36V28Fx family now becomes our recommended alternative to the slightly smaller D24V22Fx if you need a little more power or operation above 36 V:

Comparison of the maximum continuous current of Step-Down Voltage Regulators D36V28Fx and D24V22Fx.

The D24V22Fx still outperforms the D36V28Fx when it comes to dropout voltage and quiescent current:

Comparison of the dropout voltage of Step-Down Voltage Regulators D36V28Fx and D24V22Fx.

Comparison of the quiescent current of Step-Down Voltage Regulators D36V28Fx and D24V22Fx.

Introductory special

As usual, we are offering an extra introductory special discount on these new regulators, to help share in our celebration of releasing a new product. The first hundred customers to use coupon code D36V28XINTRO can get up to three units for just $7.77 each!

New Tic T500 revision to address problem with missed steps

via Pololu Blog

One of the fun things you learn as an engineer is that physically laying out a circuit requires a lot more than simply confirming it matches the schematic. In practice, there are many more things to think about, and if you’ve seen datasheets with layout guidelines or recommendations, you’re probably aware of some of them. (Thermal considerations, adequate decoupling, minimizing parasitic inductance and capacitance…) What’s more, these considerations are often in conflict (e.g. is it better to have the decoupling capacitor closer to the IC or to have a wider trace for that high-current path?), and trouble can arise if you don’t correctly assess their relative importance. That is what happened to us with our Tic T500 stepper motor controller, where the location of a specific decoupling capacitor ended up being far more significant than we had anticipated.

The problem with our original Tic T500—as we found after a customer reported having issues—was that the driver sometimes seemed to reset and lose its position in its indexing table, causing the stepper motor to stutter and skip steps. This only happened under certain conditions, and it appeared to occur more often with low-resistance and low-inductance motors, high input voltages, and high current limits.

These oscilloscope captures show the difference between normal operation and the problematic behavior on the Tic (pink is the current in one motor coil, yellow is the voltage on the driver’s STEP pin). But even without a scope, it’s apparent when the problem occurs: you can see, hear, and feel the motor jolting and moving erratically.

Unlike blatant mistakes in the design of a board that prevent it from working at all, this type of problem can be difficult to detect since a very specific combination of factors needs to be present for it to occur. When we develop a new board that might be used in a wide range of conditions, we try to cover as much of that range as possible in our testing. For example, each of our switching voltage regulator designs goes through a characterization process that involves sweeping over the full input voltage range at many different loads while looking for instability in its output voltage. Some problems are resolved by more careful selection of component values, but occasionally, we have to do additional board revisions, sometimes even going to higher layer counts, before making a product available for sale. Unfortunately, we did not encounter the problem with the Tic T500 in our initial testing.

Our first indication that something might be wrong came last month when someone posted on our forum about some strange behavior they were observing, and we started trying to replicate the issue here. In an effort to understand what was happening, we duplicated the design of the Tic using an A-Star and an MP6500 carrier board (which has the same driver the Tic T500 uses) on a solderless breadboard. The expectation was that the relatively crude breadboard layout would make the problem worse by adding all sorts of stray capacitance, inductance, and contact resistance, and that would give us some better insight, but we were unable to reproduce the problem with this setup. This pointed to the issue being something subtle about the layout of the Tic rather than some fundamental error in its routing.

After trying various different modifications to the Tic T500, we found that we could reduce or eliminate the resets and skipped steps by adding extra capacitors near one of the driver’s VIN (motor voltage input) pins. We subsequently revised the PCB to include footprints for those additional capacitors, and that seems to have solved the problem. The left picture below shows the original PCB with a capacitor we added while tracking down this problem, and the right picture shows the new revision with that capacitor added in a classier way:

This picture indicates where all the VIN capacitors and pins are on all three boards:

Surprisingly, the new capacitor on the top side of the board (indicated by the dashed outline) actually seems to be much more effective, which is unfortunate, because it limits how big of a heat sink you can add there. Even though it is basically in the same place as the one visible on the bottom side on the board, the top-side capacitor alone was enough to prevent the resetting and skipping in our tests, while the bottom-side one alone did not.

One reason we designed our basic MP6500 carrier first was to make sure we had a good understanding of the driver before designing it into more complicated products, so it was more than a little frustrating when the same basic layout that worked on the carrier didn’t work on the Tic. Initially, we assumed the difference was due to the MP6500 carrier having a 4-layer PCB compared to two layers on the Tic T500, which generally lets everything be better connected, and that could still be a big part of the answer. However, while making the comparison image above, we realized the MP6500 IC is actually rotated 180° on the carrier compared to the Tics (the text on the IC is upside down on the carrier and right side up on the Tics). So the two 0.1 μF capacitors on the carrier are closer to the “bottom” of the chip, while the two on the original Tic are closer to the “top”. If the chip is sensitive to a lack of capacitance near the bottom VIN pin, maybe that helps explain the behavior we saw!

Even though we expect it to be somewhat rare for customers to encounter this problem on the Tic T500 (to my knowledge, we have only heard of two cases), we want to make sure our products represent our best work, so we’ve pulled all our stock of the original boards (tic03a), and we’re offering free replacements for any that have already been sold. If you bought a Tic T500 from us directly, we will be emailing you to let you know how to replace it with an updated board (tic03b), or you can just contact us directly for a replacement. We will also be working with our distributors to get them replacement units for any customers that got the original Tic T500.

New product: STSPIN220 Low-Voltage Stepper Motor Driver Carrier with 1/256 microstepping

via Pololu Blog

I am happy to announce our first new product of 2019, a carrier board for the STSPIN220 stepper motor driver, which operates all the way down to 1.8 V, making it our lowest-voltage stepper motor driver. And like its higher-voltage sibling, the STSPIN820 that we released a few months ago, it offers microstepping down to 1/256 steps. This new carrier board has the same 16-pin, 0.6″ × 0.8″ form factor as our other popular stepper motor drivers, and as with our STSPIN820 carrier, it inverts the enable input so that it has the more familiar functionality of those drivers (but be careful not to pop these into a 12 V or 24 V socket!).

By the way, keep in mind that you do not necessarily need a low-voltage stepper motor driver just because your stepper motor has a low rated voltage. The voltage rating is just the voltage at which your stepper motor will draw its rated current, and it’s really the current rating that you need to be careful about if you want to avoid damaging your stepper motor. All of our stepper motor drivers let you limit the maximum current, so as long as you set the limit below the rated current, you will be within spec for your motor, even if the voltage exceeds the rated voltage. In general, using a high supply voltage along with active current limiting allows for better performance, so the main reason for using a low-voltage stepper motor driver like the STSPIN220 is if your supply voltage is constrained to some low value by some other aspect of your system.

This new release brings our selection of stepper motor drivers in this compact form factor to eleven:


A4988
(original)

A4988,
Black Ed.

DRV8825

DRV8834

DRV8880

MP6500,
Pot. CC

MP6500,
Digital CC

TB67S279­FTG

TB67S249­FTG

STSPIN­820

STSPIN­220
Driver chip: A4988 DRV8825 DRV8834 DRV8880 MP6500 TB67S279­FTG TB67S249­FTG STSPIN­820 STSPIN­220
Min operating voltage: 8 V 8.2 V 2.5 V 6.5 V 4.5 V 10 V 10 V 7 V 1.8 V
Max operating voltage: 35 V 45 V 10.8 V 45 V 35 V 47 V 47 V 45 V 10 V
Max continuous current per phase:(1) 1 A 1.2 A 1.5 A 1.5 A 1 A 1.5 A 1.1 A 1.6 A 0.9 A 1.1 A
Peak current per phase:(2) 2 A 2.2 A 2 A 1.6 A 2.5 A 2 A 2 A 4.5 A 1.5 A 1.3 A
Microstepping down to: 1/16 1/32 1/32 1/16 1/8 1/32 1/32 1/256 1/256
Board layer count: 2 4 4 4 4 4 4 4 4 4
Special features: high current low-voltage
operation,
high current
AutoTune,
digital current
reduction
high current digital current
control,
high current
Auto Gain Control,
ADMD,
high max voltage
Auto Gain Control,
ADMD,
high max voltage,
high current
128 and 256
microsteps,
high max
voltage
64, 128, and
256 microsteps,
low-voltage
operation
1-piece price: $5.95 $7.49 $8.95 $5.95 $6.95 $5.95 $5.95 $7.75 $9.95 $7.75 $5.95
1 On Pololu carrier board, at room temperature, and without additional cooling.
2 Maximum theoretical current based on components on the board (additional cooling required).

Last year, we began offering introductory specials to celebrate each newly released product, and we are continuing with that this year: the first 100 customers that use coupon code STSPIN220INTRO can get up to five units at just $3.77 each.