This is the fourth post in a series documenting the installation and first year of operation of Pololu’s 305 kW solar array. Here are the previous posts:

• Part 1: background starting in late 2022 and how we committed to the $650,000 project by the beginning of January 2023, with a target completion date of May 31, 2023.
• Part 2: installation from January 2023 through first day of operation on October 5, 2023.
• Part 3: System failures and production results during the first year of operation.

In this post, we will look at how our solar installation affected our electricity bills. Because operations were so dramatically altered by the pandemic starting in 2020, we have to go back to 2019 for the best baseline for electricity consumption and cost. To maximize the scientific rigor of our observations, we changed as many variables as possible since then, including: Continued…

We just released several small reverse voltage protection and ideal diode boards that can protect your projects from reverse voltage application. We have reverse-voltage protection built into many of our products, and we usually implement it using a P-channel MOSFET, like this:

Reverse-voltage protection using a P-channel MOSFET.

This approach is usually more efficient than just using a diode since the MOSFET has a lower voltage drop across it. However, P-channel MOSFETs have worse on-resistances than N-channel MOSFETs of similar prices and sizes. This has not mattered much for our lower-powered products, but that limitation is becoming more apparent as we are developing more products with maximum operating voltages over 40 V. The next common MOSFET voltage above 40 V is 60 V, and at that voltage and with currents above around 10 A, it starts becoming more size-efficient to use an N-channel MOSFET plus an extra chip to manage the additional complexities of controlling the N-channel MOSFET in this kind of application. This is how that circuit looks:

Schematic diagram of the Pololu Reverse Voltage Protector.

Since we are planning on using this approach on several new products, we decided to make standalone product versions as well. Here are how the first products look, using 3×3 mm MOSFETs:

This lets us get up to about 10-12 amps continuous current and an operating range of 4-60 V, which is perfect for most of our products. We tried to make the board as small as possible, and for the input and output connections we are using a new slot approach that lets the boards work with standard 0.1" headers or connectors, 3.5 mm connectors, and 5 mm connectors.

Examples of various connectors that can be used with the Pololu Reverse Voltage Protectors (from left to right: 5mm terminal blocks, 3.5mm terminal blocks, 0.1″ headers).

Texas Instruments offers two similar parts for the MOSFET controller. The LM74500 offers the same functionality as the simple P-channel MOSFET, allowing current to flow in both directions as long as the polarity is correct. This is useful for applications such as motor drivers where we want power to be able to flow back from the motor into the battery. There is also the LM74700 version, which makes the circuit function as an ideal diode, allowing current to flow in only one direction. We are offering our boards with both controller options and with two MOSFET options, for a total of four product versions:

The datasheets for the LM74500-Q1 reverse voltage protection controller and LM74700-Q1 reverse voltage protection ideal diode controller provide additional information about adding a transient voltage suppressor (TVS) diode across the input as part of a more general input protection circuit. We have pads for an SMB-size TVS on the back side of the board for those interested in adding this kind of protection:

As with our other electronics products, we make these at our Las Vegas, Nevada headquarters, so we can build custom versions with that TVS populated with a part of your choice (typical minimum quantities to make that worthwhile are around 200 pieces).

Are these interesting products? Would you want to see higher-current versions with bigger MOSFETs? Let us know in the comments or on our X and Facebook posts.

Introductory special discount! Try some out for as low as $1.16 each using our introductory special coupon, RVPINTRO (limit 5 per version)!

Related products

	Pololu Ideal Diode Reverse Voltage Protector, 4-60V, 12A
	Pololu Ideal Diode Reverse Voltage Protector, 4-60V, 10A
	Pololu Reverse Voltage Protector, 4-60V, 12A
	Pololu Reverse Voltage Protector, 4-60V, 10A

Over the last two days, I attended the 2024 Western Regional Meeting of ECEDHA, the Electrical and Computer Engineering Department Heads Association. It was held this year at UNLV, which is only 3 miles (5 km) away from Pololu, in the engineering department’s new Advanced Engineering Building that was just opened earlier this year.

UNLV’s new Advanced Engineering Building, November 2024.

I was there representing Pololu as one of five local industry sponsors. The larger companies there were treating it more like a recruiting event, and while we have several UNLV alums working at Pololu along with half a dozen student interns from UNLV, I looked at the event more as an opportunity to meet some of our customers. I also got to see some of UNLV’s new facilities for engineering students and researchers. Continued…

This is the third post in a series detailing our experience over the past two years installing and operating a 305 kW array of 630 solar panels on our building in Las Vegas, Nevada. Here are the previous posts:

• Part 1: background starting in late 2022 and how we committed to the $650,000 project by the beginning of January 2023, with a target completion date of May 31, 2023.
• Part 2: installation from January 2023 through first day of operation on October 5, 2023.

I left off with our first look at the SolarEdge monitoring site on October 5, 2023. It’s nice to see nearly real-time generation results and status. The SolarEdge P1101 optimizers connect to pairs of solar panels, so that is the resolution we can see in the array. Here is a close-up as I write this at 10AM on October 31, 2024, with a section affected by the shadow from an air conditioner circled:

SolarEdge monitoring site solar panel array close-up at 10AM on October 31, 2024.

The 1.0.72 pair of panels and 1.0.19 pair of panels at around 130 Wh so far today have generated only about half as much as the nearby panels not affected by the shadows. Continued…

This is the second post in a series detailing our experience over the past two years installing and operating a 305 kW rooftop solar system on our building in Las Vegas, Nevada. In the first post, I covered some of the background starting in late 2022 and how we committed to the $650,000 project by the beginning of January 2023, with a target completion date of May 31, 2023. This post covers how the actual installation went. Continued…

We just released the new D45V1ExFx line of small voltage regulators that can efficiently deliver up to 100 mA from input voltages up to 65 V. The small size, high efficiency, and wide input voltage range make these especially worth considering for low-power projects involving wildly fluctuating sources such as solar panels (you can see from my post yesterday that I have had solar on my mind lately) and other energy harvesting technologies. You might also just want the peace of mind of having the extra input voltage margin on something like a 24 V project that might have occasional spikes from something electrically noisy also being supplied by the same line. Or you might just have a few of these around for their small size and high efficiency at low currents.

Typical efficiency of the Step-Down Voltage Regulator D45V1ExF5.

(The 70-90% efficiency by itself is not particularly notable, but that efficiency is maintained to output currents of a few mA, which is kind of special.)

We are offering basically the same regulator circuit in two form factors. The D45V1E1Fx family has components on both sides of the PCB and measures just 0.3″ × 0.5″, making them our smallest step-down regulators.

D45V1E1Fx step-down voltage regulator basic dimensions with US quarter for size reference.

The larger D45V1E2Fx versions take up twice the area at 0.5″ × 0.6″, but they are thinner and, more importantly, offer two extra pins, including a precision enable input that can be used to set a cutoff voltage.

D45V1E2Fx step-down voltage regulator pinout.

We have a 1 MΩ pull-up resistor on the enable input, which means that if you pull that line low, you will lose about 1 μA per volt on your input. At higher input voltages, this current is higher than the quiescent (no-load) current the regulator consumes, so if you are just powering a microcontroller with a low idle or sleep current, you might be better off just using those low-power states to save energy, but if your load continuously draws more current, the shutdown feature could help prevent over-discharging your battery.

As with our other electronics products, we make these at our Las Vegas, Nevada headquarters, so we can quickly customize them for other output voltages besides our stock versions of 3.3 V, 5 V, and 12 V (depending on the customization, we can usually do custom production runs for setup fees starting around $250).

Introductory special discount! Try some out for only $3.33 each using our introductory special coupon, D45V1EXINTRO (limit 3 per version)!

Related products

	12V, 100mA Step-Down Voltage Regulator D45V1E2F12
	5V, 100mA Step-Down Voltage Regulator D45V1E2F5
	3.3V, 100mA Step-Down Voltage Regulator D45V1E2F3
	12V, 100mA Step-Down Voltage Regulator D45V1E1F12
	5V, 100mA Step-Down Voltage Regulator D45V1E1F5
	3.3V, 100mA Step-Down Voltage Regulator D45V1E1F3

October 2024 marked one year of operation of our 305 kW rooftop solar power generation system. In this series of posts, I will reflect on our installation and operation experience over the past two years to try to assess whether it was worth it. This first post covers some background leading up to the project and the overall system design. I will detail the installation process, the first full year of operation, and the production and financial results in subsequent posts. Continued…

We are pleased to announce that Pololu is now an authorized Dobot distributor, and our first offering from their catalog is a robot arm that we are especially excited about: the Dobot MG400 Desktop Cobot Robotic Arm. The Dobot MG400 is a departure from products typically available from Pololu. While the 8 kg (17 lb) unit is small for the collaborative robot world, it is much larger than typical Pololu products, and the cost is correspondingly higher as well. However, the price is still very competitive for what the robot arm offers, as the high ±0.05 mm positional repeatability, collision detection, and drag-to-teach ability make this cobot a compelling option for serious automation applications. With a footprint of 19 cm (7.5 in) square, the small size and low cost also make the Dobot MG400 accessible to many education and research applications that need more than a toy or hobby product. The following video shows off some of the arm’s features:

The Dobot MG400 has a maximum reach of 44 cm and can rotate through 320°, and it can lift payloads up to 500 g (18 oz). Dobot makes a sliding track module that substantially expands the operating envelope of this robot and a vision system, which are also available through Pololu (product pages for those are coming soon).

Motion range of the Dobot MG400 Desktop Cobot Robotic Arm, profile view.

Motion range of the Dobot MG400 Desktop Cobot Robotic Arm, top view.

The picture below shows all of the accessories included with the MG400:

Accessories included with the Dobot MG400 Desktop Cobot Robotic Arm.

Please note that this arm does not include any grippers, but it does include a general-purpose flange for mounting end effectors that can be purchased separately from Dobot or other suppliers, or you can 3D print your own. A suction nozzle is included, but it requires an external air supply (compressor not included) to function.

The MG400 can be programmed a variety of ways, including through drag-to-teach positioning, a graphical programming interface, and Lua scripting. The controller in the base has plenty of I/O that makes it easy to integrate the robot into a bigger system.

The pictures below show example MG400 applications with custom 3D-printed electromagnet end effectors used to manipulate Micro Metal Gearmotors for packaging and testing.

Related products

Dobot MG400 Desktop Cobot Robotic Arm

We are excited to introduce our new series of stepper motor drivers based on the Allegro A5984 that offer an easy way to control bipolar stepper motors from supply voltages between 8 V and 40 V (absolute max). It’s hard to believe it’s been 15 years since we introduced the original A4983 stepper motor driver carrier in the small 16-pin form factor that would become ubiquitous for stepper motor drivers. We updated the product in 2011 when Allegro released the newer A4988, but since then we have released boards for stepper motor drivers from other semiconductor manufacturers, including Texas Instruments (most notably the DRV8825, and DRV8834, and more recently the DRV8434 series), Monolithic Power Systems (MP6500), STMicroelectronics (STSPIN820 and STSPIN220), and Toshiba (TB67S249FTG and TB67S279FTG). The new Allegro A5984 carriers, which can be used as drop-in replacements for the A4983/A4988 in many applications, bring us full circle with those original drivers, and with support from Allegro, we are able to offer them at extra low prices.

Minimal wiring diagram for connecting a microcontroller to an A4988 stepper motor driver carrier (full-step mode).

Minimal wiring diagram for connecting a microcontroller to an A5984 Stepper Motor Driver Carrier, Adjustable Current, Blue Edition.

As with our other stepper driver products, we are offering the A5984 carriers with small trimmer potentiometers for setting the current limit. However, these can be a little fiddly to work with, so we are also offering several fixed-current versions for cases where you just want a particular set point without having to tune each board (for volume applications, we can do custom production runs with whatever set point you need). We also have two PCB options—a standard 2-layer version that is most economical for lower-current applications, and a 4-layer “Blue Edition” for maximum performance that can deliver up to 1.2 A continuous per phase (heat sinks and active air flow can bump that higher). The following table shows all the options:

	Adjustable Current, Blue Edition	Adjustable Current	Fixed 1.5A@5V / 1A@3.3V, Blue Edition	Fixed 1A@5V / 660mA@3.3V, Blue Edition	Fixed 750mA@5V / 500mA@3.3V	Fixed 500A@5V / 330mA@3.3V
Current limit (VDD = 5 V):	adjustable (potentiometer) 1.2 A max continuous 2 A peak*	adjustable (potentiometer) 1 A max continuous 2 A peak*	1.5 A*	1 A	750 mA	500 mA
Current limit (VDD = 3.3 V):			1 A	660 mA	500 mA	330 mA
Available versions:	no header pins headers soldered	no header pins headers soldered	no header pins headers soldered	no header pins headers soldered	no header pins headers soldered	no header pins headers soldered
PCB layers:	4	2	4	4	2	2
Price without header pins:	$3.97	$3.75	$3.75	$3.75	$3.49	$3.49
Price w/headers soldered:	$4.97	$4.75	$4.75	$4.75	$4.49	$4.49
* This current exceeds what the module can deliver continuously and is only achievable for short durations or with sufficient additional cooling (e.g. adding heat sinks or active air flow).

Compared to those original A4988s, the A5984 carriers offer a number of improvements, including a higher maximum operating voltage, more microstep options and higher-resistance current sense resistors for improved microstepping performance, a fault output for reporting over-current faults, and an adaptive decay current control algorithm that automatically adjust the amount of fast decay to optimize the motor current waveform.

Introductory special discount! To celebrate the release of the A5984 carriers, the first hundred customers to use coupon code A5984INTRO can 15% off up to five units of each!

The following tables show our full selection of 16-pin stepper motor drivers:

	STSPIN­220	DRV8834	A4988 (original)	A4988, Black Ed.	MP6500, Pot. CC	MP6500, Digital CC	A5984	A5984, Blue Ed.
Driver chip:	STMicro STSPIN­220	TI DRV8834	Allegro A4988		MPS MP6500		Allegro A5984
Min operating voltage:	1.8 V	2.5 V	8 V		4.5 V		8 V
Max operating voltage:	10 V	10.8 V	35 V		35 V		40 V
Max continuous current per phase:(1)	1.1 A	1.5 A	1 A	1.2 A	1.5 A		1 A	1.2 A
Peak current per phase:(2)	1.3 A	2 A	2 A		2.5 A	2 A	2 A
Microstepping down to:	1/256	1/32	1/16		1/8		1/32
Board layer count:	4	4	2	4	4		2	4
Special features:	low input voltage	low input voltage				digital current control	versions also available with fixed current limits
Available with headers soldered?:	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1-piece price:	$7.95	$7.95	$4.49	$4.95	$6.95	$6.95	$3.75	$3.97
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).

	STSPIN­820	DRV8825	TB67S279­FTG	TB67S249­FTG	DRV8434	DRV8434A	DRV8434S, Pot. Max.	DRV8434S, 2A Max.
Driver chip:	STMicro STSPIN­820	TI DRV8825	Toshiba TB67S279­FTG	Toshiba TB67S249­FTG	TI DRV8434	TI DRV8434A	TI DRV8434S
Min operating voltage:	7 V	8.2 V	10 V	10 V	4.5 V	4.5 V	4.5 V
Max operating voltage:	45 V	45 V	47 V	47 V	48 V(3)	48 V(3)	48 V(3)
Max continuous current per phase:(1)	0.9 A	1.5 A	1.1 A	1.6 A	1.2 A	1.2 A	1.2 A
Peak current per phase:(2)	1.5 A	2.2 A	2 A	4.5 A	2 A	2 A	2 A
Microstepping down to:	1/256	1/32	1/32	1/32	1/256	1/256	1/256
Board layer count:	4	4	4	4	4	4	4
Special features:			Auto Gain Control, ADMD	Auto Gain Control, ADMD	6 decay modes with 2 smart tune options	Stall detect, smart tune ripple control decay	SPI control, stall detect, 8 decay mode options
Available with headers soldered?:	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
1-piece price:	$14.95	$15.95	$10.75	$12.95	$9.95	$12.95	$12.95	$12.95
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). 3 Not recommended for use with 48V batteries, which can be well above nominal when fully charged.

Related products

	A5984 Stepper Motor Driver Carrier, Adjustable Current, Blue Edition
	A5984 Stepper Motor Driver Carrier, Adjustable Current, Blue Edition (Soldered Header Pins)
	A5984 Stepper Motor Driver Carrier, Adjustable Current
	A5984 Stepper Motor Driver Carrier, Adjustable Current (Soldered Header Pins)
	A5984 Stepper Motor Driver Carrier, Fixed 1.5A@5V / 1A@3.3V, Blue Edition
	A5984 Stepper Motor Driver Carrier, Fixed 1.5A@5V / 1A@3.3V, Blue Edition (Soldered Header Pins)
	A5984 Stepper Motor Driver Carrier, Fixed 1A@5V / 660mA@3.3V, Blue Edition
	A5984 Stepper Motor Driver Carrier, Fixed 1A@5V / 660mA@3.3V, Blue Edition (Soldered Header Pins)
	A5984 Stepper Motor Driver Carrier, Fixed 750mA@5V / 500mA@3.3V
	A5984 Stepper Motor Driver Carrier, Fixed 750mA@5V / 500mA@3.3V (Soldered Header Pins)
	A5984 Stepper Motor Driver Carrier, Fixed 500mA@5V / 330mA@3.3V
	A5984 Stepper Motor Driver Carrier, Fixed 500mA@5V / 330mA@3.3V (Soldered Header Pins)

We are having a Labor Day sale through Tuesday, September 3! Check out the sale page for more information. Please note that we will be closed Monday, so orders placed after 2 PM Pacific Time Friday, August 30 will be shipped on Tuesday, September 3.