Engage Your Brain (Page 4)
A blog by Pololu president Jan Malášek. For more information, please read the first post.
Since my last post about free shipping in the USA, we expanded the program to include orders consisting of $40 or more in free add-on shipping items. And today, we added almost 300 different metal gearmotors to our selection of products that ship for free in the USA. (Don’t worry, we don’t pile up actual good production motors like we did in that picture; those were returned by an infamous, once-skyrocketing startup.)
I am excited to announce our first voltage regulators with multi-turn trimmer potentiometers! I have wanted to add multi-turn pots to our products for a long time, but the problem has been that they are really expensive. They also tend to be quite big, at least compared to many of our boards, which we try to keep compact, and the smaller, surface-mounted ones are especially expensive. My latest round of looking for lower-cost options did not pan out, but I decided to just give it a try with the expensive parts.
The new S9V11x regulators that feature these potentiometers are buck-boost regulators that can output a voltage that is lower, the same, or higher than the input voltage. There are also versions with a multi-turn pot for adjusting the undervoltage cutoff threshold, so that if you use these with batteries, you can prevent overdischarging them. With twelve turns of adjustment available, it’s much easier to precisely set the voltages on the modules than with the single-turn potentiometers we have used on other adjustable regulators.
The output and cutoff multi-turn adjustment potentiometers on the S9V11x voltage regulators.
While I have been talking mostly about the potentiometers, the main regulator is pretty magical, too, giving you quite a bit of power over a broad operating input range in a small size.
Typical maximum continuous output current of Step-Up/Step-Down Voltage Regulator S9V11x
Our stock products are available in several combinations of adjustable and fixed output voltage and cutoff. If you have a higher-volume application, we can make them with fixed voltages wherever you need them. You could initially prototype your design with the adjustable version and then get fixed ones made once you know exactly what voltage you need.
|Regulator||Input (V)||Output (V)||Low-voltage cutoff||Size||Price|
|#2868 S9V11MACMA||2* – 16||2.5 – 9 (fine-adjust)||fine-adjust||0.50″ × 0.60″ × 0.25″||$11.95|
|#2869 S9V11MA||2.5 – 9 (fine-adjust)||–||$8.95|
|#2870 S9V11F5S6CMA||5 (6 V selectable)||fine-adjust||$8.95|
|#2871 S9V11F3S5CMA||3.3 (5 V selectable)||fine-adjust||$8.95|
|#2872 S9V11F3S5||3.3 (5 V selectable)||–||0.50″ × 0.60″ × 0.17″||$5.95|
|#2873 S9V11F3S5C3||3.3 (5 V selectable)||3 V (fixed)||$5.95|
|#2836 S9V11F5||5||–||0.30″ × 0.45″ × 0.17″||$5.95|
|* The regulator has a minimum start-up voltage of 3 V, but it can operate down to 2 V after startup. It is disabled when the input voltage is below the low-voltage cutoff.|
I am very interested to see what people think of the multi-turn adjustment feature. If these new regulators sell decently or customers ask for it, we will add the multi-turn potentiometers to our other regulator offerings. Is the extra expense worth it? Or do you know of a good, low-cost, multi-turn potentiometer we could consider for future products like this?
Some of my happiest memories of building Pololu, and therefore of my life, are of my friends Ben and Paul moving to Las Vegas to work on it with me. Ben was my best friend in high school, but we had not stayed in touch well after that. I met Paul at MIT, and he was involved with Pololu from the beginning, in 2000, and after he graduated, he visited Candice and me in Massachusetts and then in Las Vegas from time to time. Ben and I reconnected in late 2006, and he moved to Las Vegas shortly thereafter; Paul finally joined us (with his wife Fang) full time after the summer of 2007.
So we have been at this as a team for over ten years now. It’s long enough that it’s difficult to remember things being different. As I started writing this, I figured that our first Black Friday sale must have been in 2007, too. But apparently we did not have our first one until 2009 (though Ben pointed out, with a hint of resentment, that he might have been pushing for it sooner). I have happy memories of last-minute sale preparations and then staying up past midnight to watch the sales come in, wondering how long the doorbuster deals would last. Some years we were at home, instant-messaging each other; other years, we were at the office making sure everything worked as expected.
Even now, our Black Friday/Cyber Monday sale is probably the project Paul, Ben, and I work on together most intensely. There are of course others involved in getting ready for the sale, and there are lots of other projects the three of us all work on. But there’s a really hard deadline, which we typically do not have to deal with, which leads to late nights together. And preparing for the sale involves deciding which products we care about a lot and that we want to highlight, and since it’s our company, it’s our call on how much we want to push by offering products at or sometimes below cost, in the spirit of not only merchandising but also good fun. It’s a time to look back on the products we have released this year, and, as I am doing now, reminisce about Black Friday sales past.
(We do not recommend actually running a Balboa in the snow.)
I am giving this background not only to share some of what I am thankful for, but to give our customers and newer employees some understanding of our perspective and what goes into these sales. It’s personal. It’s something fun for me, a kind of reversal of the excitement of looking for good deals as a shopper on Black Friday. When I used to be more directly involved in getting things made and shipped, I would usually go to stores in the evening, to see what deals might be left that other shoppers weren’t interested in. In the past few years, I’ve had the luxury of doing some brick and mortar Black Friday shopping in the morning, though usually I’m still shopping for things like vacuum cleaners for Pololu at stores like Home Depot.
We listen to what our customers say, and we try to put something in our deals for everyone. Of course, part of the point is to offer some extreme discounts, so we limit the quantities and the durations on those deals. But we still try to set the limits such that the doorbusters will last at least a few hours, so if you care and try a little, they should be available. If you’re one of those people who don’t like waking up early or sorting through special offers, I remind you that we work hard to offer good prices to begin with, and we are offering discounts site wide for the duration of the sale. And if you are a student or parent who really had your heart set on a Zumo or Balboa robot for Christmas but miss out on the doorbuster for some reason, and that extra discount makes the difference in being able to afford it, let us know. We want deserving people to have these robots, and we’ll try to help you out.
Now, on to details about the sale this year, since we will be making some big changes from years past. In a break from past years, when we had a single set of doorbuster coupons that went active on the first day of the sale and the same items were on sale for the duration of the sale (Wednesday before Thanksgiving through Cyber Monday), we will have different door busters for different days. We have also upgraded our coupon system so that we can control the time they are active, not just the day, so that we can make doorbusters go active at a time more appropriate for our customers in the United States.
Our new free shipping system should allow many of the sale items to ship for free or at a low cost, which should make it practical to make several orders over the course of the sale. We might combine some orders into single shipments to reduce our shipping expenses, but please note that because of the volume of orders we get during the sale, we will not be able to accommodate requests to combine orders to reduce shipping charges.
I hope you get to spend the holidays doing things that bring meaning to your life, with the people you love.
Oh, and if you were expecting to see a preview of the sale, it’s up on the Black Friday/Cyber Monday sale page now. Keep checking back throughout next week as we reveal more great deals!
We sell a lot of motor drivers, which makes sense since you usually need motors to build robots, and motor drivers tend to be the kind of product you cannot really build yourself on a breadboard. One of our more popular products is the dual VNH5019 shield for the Arduino:
Pololu dual VNH5019 motor driver shield, assembled and connected to an Arduino Uno R3.
Older version of the High-Current Motor Driver Carrier.
When I first heard of the chip (at one of the first LVBots meetings), it seemed like someone must have misremembered the spec since it was inconceivable for a single integrated chip to deliver 30 amps. And to some extent, that was valid—you would have to do a lot of extra thermal management work to get 30 A out of that chip without it overheating. But the chip really could do in excess of 10 A, which was still amazing; the real limitation was in voltage, especially if you tried to use PWM at any moderate frequency. The VNH2SP30 was better about PWM frequency, letting us get to 20 kHz, but it had an upper operating limit of 16 V. The VNH5019 raised this to 24 V, getting us tantalizingly close to the 24V rail many would like to use. The problem is that 24 V is the limit, and we really need to be able to operate higher than that to account for the usual variations in nominally 24V power setups.
As far as I know, there is no integrated circuit that can deliver over ten amps at 24 V nominal (i.e. at least 30 V max); for that kind of power, you need to go to H-bridges with discrete MOSFETs. We have had those as stand-alone products for a while, too. But those still leave you with a lot of wiring to do if you want to drive two motors, which is typically the minimum for a mobile robot. The new product family we just released makes that easy by providing two high-power motor drivers in one Arduino shield-type package:
As you can see from the pictures, the main difference in these Dual G2 High-Power Motor Driver Shields is in the MOSFETs: the white boards have larger, 5×6mm MOSFETs, and the blue boards have smaller, 3×3mm MOSFETs. These correspond to the two versions of the individual drivers:
Pololu G2 High-Power Motor Driver 24v21 and 24v13.
(The higher-power version on the left has the MOSFETs on the back side of the board.) We also offer each board with 30V and 40V MOSFETs, for four total options. The new dual motor drivers perform similarly to our single-channel G2 units, and like the single channel carriers, all of these dual drivers feature current sensing and an adjustable current limit that could be used to detect and protect against stall conditions. These are the individual performance points:
Dual G2 High-
Power Motor Driver
Dual G2 High-
Power Motor Driver
Dual G2 High-
Power Motor Driver
Dual G2 High-
Power Motor Driver
|30 V||40 V|
|18 V||28 V|
current per channel:
|22 A||18 A||18 A||14 A|
|Default active current-
|60 A||50 A||40 A|
|10 mV/A||20 mV/A|
For drivers like these, power (heat) dissipation is generally the limiting factor. The copper area around the MOSFETs on both the white and blue versions of the drivers are about the same, so the lower-current blue units perform better then their smaller single channel G2 counter-parts, while the higher current white drivers do worse than the smaller single channel G2 carriers (which also use four layer PCBs for better performance). The power ratings we provide are the maximums without additional heat sinking or air flow and at room temperature. Please note that the boards will be extremely hot at those maximum currents, and the available current will be lower if the ambient temperature is higher.
Since many Arduino boards do not support higher input voltages, the new dual drivers also incorporate a 1A switching regulator so that a single higher-voltage supply can power the motors and Arduino. We have an Arduino library to help you get up and running quickly. And for those who want to use the board without an Arduino, all of the motor control connections are also brought out to a row of 0.1″ headers on one side of the board.
(And for those of you wanting to use this kind of driver with a Raspberry Pi, we have a Raspberry Pi HAT form-factor version coming soon!)
We are now offering free US shipping for $60 or more of Pololu-branded products with active statuses.
Since my post on Thursday afternoon, we have brought free shipping to dozens of products and free add-on shipping to hundreds more. Unfortunately, that still does not get you really free shipping for most of our thousands of products because many of them are individually too low-cost to make part-by-part free shipping feasible. We just do not have a way to ship you a $6 regulator or an $8 pair of wheels for free without having to inflate the price of the products. But today, we released phase two of our free shipping initiative, which allows us to offer free shipping in the US on orders of $60 or more of Pololu-branded products that have an active status. This should bring free shipping to most of our typical orders, which might include that set of wheels, a few motors, a motor driver, and maybe the $6 regulator.
You might be wondering what I meant by that somewhat awkward phrase, “Pololu-branded products that have an active status”. That’s actually related to yet another exciting new set of features we are bringing to the Pololu site. We are proud that we design and manufacture most of our products, and we want to make it easy to tell which items are made by us. For products from other brands, especially where we are authorized distributors or otherwise working with those brands, we want to make it clear that you are getting the product from that brand, and not some counterfeit or knock off. And sometimes we all just want something generic, like the ubiquitous 0.1" headers, where the manufacturer or brand does not really matter. In some of those cases, we might not want to reveal our suppliers, or we might want to have the flexibility to change suppliers without updating product specifications; explicitly calling out a product as generic should help make it clear what kind of a product you are getting.
Because many of our customers build their own products using our products as components, or design curricula around our products, I also want to better communicate the life cycle status of our products. We therefore added a “product status” field to our product listings so that you can quickly tell if a product is one that we expect to keep making for a long time or if we expect to be discontinuing it soon. I will go over the various product status designations in a separate blog post, but for the purposes of this free shipping announcement, the point is that the products we make and which are in our good graces will be considered toward the $60 free shipping minimum.
We will be updating the product brand and status fields for our products in the coming weeks; please let us know if a product you are interested in is not updated yet.
Everyone wants free shipping, right? Well, today I am happy to announce an important step in bringing free shipping to Pololu, at least for our US customers. We are beginning to offer free shipping in these two senses:
Free shipping within the United States
Some items are eligible for free shipping within the United States. If your shopping cart consists only of items eligible for free shipping, you will be presented with a “Free Shipping” shipping option during checkout. Free shipping will be shipped by a carrier and service we select, which will typically be the lowest-cost, slowest service. Currently, that would likely be First-Class Mail through the US Post Office or a ground service by FedEx, depending on the contents of the order.
Free add-on shipping within the United States
Some items are eligible for free add-on shipping for orders within the United States. These are typically very light items that should not significantly impact our shipping cost, and we pass on those savings to you. No additional shipping will be charged for these items, independent of your shipping method. Orders that consist only of free add-on shipping items will cost the minimum shipping cost for each service as the item sizes and weights will not be added to the shipping cost calculation. Orders with at least one free shipping item and the rest free add-on shipping items will have a free shipping option.
Because items with free add-on shipping will not be considered in the calculation, it is possible for the shipping method you select to be invalid because the package exceeds the limit for that method. In such cases, we will substitute a similar shipping method. For example, if you pay for First-Class Mail as your shipping method but your order actually ends up weighing more than the limit for First Class Mail, we would ship by Priority Mail.
By controlling these two aspects of free shipping on an individual product level, we can really offer free shipping, without raising prices. We are rolling this feature out with a few items we would like to promote:
Products initially eligible for free shipping and free add-on shipping:
Products initially eligible for free shipping only:
Products initially eligible for free add-on shipping only:
As we work on our system and monitor the results with these initial products, my goal is to make free shipping, or at least incrementally free shipping, available for more and more of our products. We still do not have a solution for those of you who write us angry emails about the ridiculousness of our charging $3.95 to ship a $2 part (and yes, I am aware of 39-cent listings with free shipping on AliExpress; for now, we cannot compete with them on price alone). But rest assured that since shipping is one of our biggest expenses, we will continue to work hard on keeping that cost as low as we can.
If you see a product that you feel should qualify for free shipping or free add-on shipping but does not, please contact us, and we can evaluate the product’s eligibility. I would also like to hear what you think of this approach and whether you expect it will be helpful to you.
Update (31 October 2017): We are now offering lots more free shipping.
It’s been more than two years since my last post. I thought I would post an update a year ago, when Eve was born, but that didn’t go very well, and the uncertainty about how things would turn out with her made it difficult to rally around her birth as some celebratory point from which to start moving on. I feel at once as if I have lost two years of my life, making no progress, and yet that my life has completely transformed in that time. But I know things have gotten better because I am usually free of the sadness and fear that still filled me a year ago, around Dez’s first birthday. Continued…
This blog post is about some personal difficulty I’m going through: last month, my baby died unexpectedly a day or two before he was born. I could just collect my thoughts in my private journal, but I am sharing my experience here on the Pololu blog because most of the people I interact with and care about are related to Pololu, be they friends, employees, vendors, or customers. Just about everyone at Pololu knew of my eager anticipation of this new baby, and any visitors were aware that I might miss our meetings with short notice depending on when the baby arrived. Continued…
Everyone wants encoders on their motors. If you think you don’t, you just don’t know it yet. I think the main reason is that we really just want motors to do what we tell them to do, but they don’t. One of the most common beginner questions we get is some variation of, “why doesn’t my robot go straight?” or “I got two of the same motor but they do not go the same speed; is something wrong with one of them?” More seasoned robot builders know that since there will always be variations in everything that contributes to a motor’s performance, our best hope is to put a sensor on the motor to monitor what is actually happening and then adjust the motor control to make reality better match our desires. Continued…
We recently substantially reduced prices on our stepper motor driver carriers, and I figured this announcement was a good time to give you an update on our perspective and capabilities.
It has been over five years since I designed our original stepper motor driver carrier, which was for the A4983 from Allegro. While fairly straightforward, the implementation reflected several design philosophies that go into Pololu products, such as making the boards as small as practical and including the right extra components to make the main chip easily usable without unnecessarily limiting its features. Continued…