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Description
WELWYN W21-91RJI Through Hole Resistor, 91 ohm, 100 V, Axial Leaded, 3 W, � 5%, W21 SeriesThe Welwyn W21 series wirewound resistors are highly stable and reliable resistors offering high power and resistance in a small size. The Resistance range includes E24 decade values from 1ohm to 10 ohm. W21 series are suitable for use in harsh environments and Ideal for protection circuits. A high purity ceramic substrate is assembled with interference fit end caps to which are welded the termination wires. The resistive element is wound on substrate
The Welwyn W21 series wirewound resistors are highly stable and reliable resistors offering high power and resistance in a small size. The Resistance range includes E24 decade values from 1ohm to 10 ohm. W21 series are suitable for use in harsh environments and Ideal for protection circuits. A high purity ceramic substrate is assembled with interference fit end caps to which are welded the termination wires. The resistive element is wound on substrate and welded to caps.
- Power rating at 25�C is 3W
- �1%, �2% and �5% tolerance
- Operating temperature range -55�C to 200�C
- Temperature coefficient is <�75ppm/�C
Applications
Industrial, Power Management, Consumer Electronics, Portable Devices
Product details
| Temperature Coefficient | � 75ppm/�C |
| Power Rating | 3W |
| Resistor Element Material | Wirewound |
| Automotive Qualification Standard | - |
| Resistance | 91ohm |
| Resistance Tolerance | � 5% |
| Product Range | W21 Series |
| Resistor Case Style | Axial Leaded |
| Voltage Rating | 100V |
Other details
| Brand | WELWYN |
| Part Number | W21-91RJI |
| Quantity | Each |
| Technical Data Sheet EN |
All product and company names are trademarks™ or registered® trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them. Image is for illustrative purposes only. Please refer to product description.
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- Free Standard Shipping on $100+ Orders to the USA.
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Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
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4.2 ★★★★★
Based on 1660 reviews
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Product Reviews
★★★★★ 5
Oooooh this little guy packs a punch!
Color: Black01
I dont know what the heck took me so long to get this little gadget. I absolutely love it and now can't imagine being without it. I can't compare it to the other big names, I just simply can't afford those! But I can tell you this little guy packs a huge punch on results!
1st I must tell you my house is vey small, maybe 1600sq ft inside, only 2 bedrooms. I have no foot traffic at all. No kids. No pets, No shoes inside-sorry thats just the way my husb & I live. So I run my Robo 2 times a week only and he still picks up massive amounts of lint, rug fibers, dust etc.... Programing is super simple, easy to change plans, various options on suction and tweaking the areas you want covered. Robotic absolutely fabulous. Don't be sketched-out on its price point. Seriously its low price is freakin worth it! Like I said I dont know how it would compare to Roomba, and I actually dont care because Roborock is amazing!!! Love Love Love it!!!!
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Reviewed in the United States on March 21, 2026
★★★★★ 1
“Terrible Product, Even Worse Support
Color: Black01
Roborock vacuum has been nothing short of exasperating, and after more than ten days of back‑and‑forth with customer support, I can confidently say this is one of the most disappointing purchases I’ve made in years. What should have been a reliable, premium home appliance turned into a daily source of frustration, and the company’s customer service only amplified the problem.
The core issue began when the vacuum repeatedly failed to complete its cleaning cycle. Instead of finishing the job, it would stop randomly in different rooms and display an “interrupted by user” message — even though no one had touched it. Firmware was up to date, the environment was unchanged, and the vacuum had been working fine before. The problem was clearly internal, whether hardware or software, but the device simply refused to function as advertised.
Unfortunately, the product’s shortcomings were only the beginning. The real ordeal started when I reached out to Roborock’s customer support. Over the course of nearly ten emails, I received little more than generic, repetitive responses that did nothing to diagnose or resolve the issue. Each day brought a single, unhelpful reply asking for information I had already provided or requesting steps that were unnecessary because the malfunction was already documented in the app. The vacuum’s cleaning history, error logs, and behavior patterns were all visible on their end, yet they continued to push the burden back onto me.
Instead of meaningful troubleshooting, I was met with delays, scripted messages, and requests to redo the same tasks over and over. At one point, they asked for logs, screenshots, timestamps, and device information — all after I had already spent days explaining the issue in detail. It felt less like support and more like a slow, circular process designed to wear the customer down.
After more than a week of this, I finally reached my limit. I had purchased a premium product expecting premium reliability and service, but what I received was a malfunctioning vacuum and a support experience that left me feeling ignored and undervalued. I eventually gave up entirely and bought a replacement from another brand just to end the frustration.
By the time Roborock finally offered a replacement, the damage was already done. The trust was gone, the patience was gone, and frankly, the brand loyalty was gone. A company’s true character shows when something goes wrong, and in this case, Roborock failed spectacularly.
In the end, the vacuum didn’t just stop cleaning my floors — it swept away any chance of me ever purchasing from this company again. Between the unreliable product and the painfully slow, ineffective customer service, I cannot recommend Roborock to anyone. There are plenty of other brands that value their customers and stand behind their products. Sadly, Roborock is not one of them.
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Reviewed in the United States on March 25, 2026
★★★★★ 5
Robo vacuum gets the job done
This is our first robot vacuum so I don't have anything to compare it to other than what friends have said about theirs.
I got this on sale for around $150. Definitely worth the price in my opinion, our floors are cleaner now! This is the Q5Pro (Q5ULE) model. This one has the features of vacuum, mop, map(with split and merge options), zones, spot clean, joystick/remote controls, no go zones, and scheduling.
Wifi setup took a couple tries. But I think that shouldn't be a problem for a lot of people. It worked fine after I turned off the VPN on my router so something was being blocked there. It was easy to follow the quick start instructions that came in the box and the directions were accurate.
The app (I have android) is pretty simple and easy to use. I put it on my kid's phone also so they can use it as needed. Used the same login as my own and it logged me out on my phone, but once I logged back in was able to have it logged in on two devices with no issues.
It will ping you when a scheduled task is completed and if it was able to complete it or ran into issues. The history feature is nice as you can see a track of where it went. It shows yellow icon in the history if there was an issue like couldn't reach a room or something else.
I told it to spot clean but it wasn't cleaning well, so I turned it over and found a twist tie in the rollers. Got that out and it did fine after that.
There is a page in the app that tracks how long till expected maintenance for the the rollers, brushes, and sensors. We have two dogs and two people with long hair so we'll have to use a seam ripper regularly to get hair off the roller ends to keep that from accumulating. It's easy to get things out of the rollers, and put them back in. You can't put them in wrong as the black and red have different shapes on the ends. The rectangle roller cover is slightly difficult to put back on, you have to hold the spring clips open so it goes back on.
Suction seems to be powerful and there are different suction settings in the app as well. It doesn't always get everything but love that it vacuums better than the job the humans were doing most of the time. Mainly has missed some larger lightweight crumbs that got flung by the arm brush and didn't get everything by the edge of the area rug on the 1 pass setting. We had party confetti of the foil variety and it got some of that up but didn't get all of it.
The charging dock is just too tall (3 7/8 inches) to go under our sofa so we'll have to figure out a good place to 'hide' the dock. The vacuum itself is about 3 1/2 inches tall in including the round port that sticks up on top. (The round port is for suction I believe, it's not sensors)
It finds the dock fine, hasn't gotten lost even when moved during cleaning. Charging is good and the app lets you sent peak/off peak charging times so it will keep it alive during the day but fully charge at night when power costs less.
Overall seems like a great vacuum. It already (less than a weekof ownership) has scuffs on the outside from rubbing on things but I have kids and they constantly move chairs, etc so it has to relearn things all the time. It is impressive in that it will lightly bump/brush but even in joystick mode it won't let you ram into things, it slows itself down before it touches anything.
I haven't tried out the mopping pad yet, it comes with a pad, water tank, and a plastic floor protector to put under the dock to keep damp off the floor until you take the mop pad off. I'm not thinking it will be super impressive as it's just going to drag a wet cloth around but I may be wrong. Will update when I've tested.
Time will tell how sturdy and robust it is but it seems to be good so far!
Edit to update: it's fine with the mopping but not a true mop, it's dragging wet and leaves wet streaks, better than nothing. We may use it some but with the steam mop I know it will actually get it clean.
I moved the dock more than 3 inches and had to remap because it threw it off. Once before I moved the dock just a smidge but more than 3 inches is too much.
If the battery gets below 20% it will return to the dock to charge, then will go finish at some point. I didn't find out what % of charge triggered the return to work.
Had it for over 3 months now and use it daily. It does good overall, happy with our purchase.
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Reviewed in the United States on February 17, 2025
★★★★★ 4
Not a great mop, but it is a great vacuum.
Color: Black01
The Roborock Q7 L5 has been a great addition to the cleaning arsenal of my home. I have a 1200sqft one story home with tile and laminate flooring, and it has essentially removed my need to vacuum every day, or even every week, and I have 6 cats. I have had it set to vacuum every night in the common areas of my home, and it is quiet enough that it does not disturb my husband and I when we are sleeping. I only have to empty it out once or twice a week.
You MUST make sure your common areas are cleaned up of debris on the floor, and to set no-go zones where you cannot clean up clutter on the floor. It WILL eat cords, shoestrings, animal toys, etc. It WILL get stuck under things, which are where no-go zones come into play.
It struggles with cleaning up litter, so I still have to sweep the floor around my cats litter boxes. However, it picks up the cat hair fairly well. It also crosses thresholds VERY well, and will vacuum my area rugs and shower mats that are not affixed to the floor with tape without sucking them up like a normal vacuum does.
Some complaints I do have with this model...
- It CANNOT be integrated into Home Assistant at this time, which was one of the things I was excited about. Something about a new firmware they started using that is not compatible with the integration starting around this model type. Unfortunate, but whatever.
- The mopping function leaves more to be desired. If you put water in the unit, it WILL leak, even if you don't have the mop mount installed or are mopping, so sometimes you end up with little water drips on the floor. I also find that it does not do a very good job at mopping at all, even with wetting the cloth first, but for tile and laminate flooring, dry mopping is fine, so I have been leaving the mop mount installed without mopping to pick up dirt and dust that the vacuum part misses.
- The filter was installed incorrectly from factory, and it took me a few weeks to realize that. I have no idea how much dust got sucked up into the motor, so definitely check that when you first get it.
- The mop cloth is poorly sewn. It maybe lasted two uses before it started falling apart. Fortunately, I sew, so it can be easily fixed, but I would have hoped that these would have been a little more high quality.
- Expect to buy more replacement parts. Especially mop cloths. You will need multiple mop cloths if you are using the roborock to mop with.
Overall though, most of my complaints are with the mopping function of this machine. Since I don't mop very often anyway, due to damaged laminate flooring, it works fine for me. Not having to vacuum the entire house every day, or sweeping the kitchen manually every time after I cook is a huge time saver. If you need a robot vacuum, and not a mop, I feel like the Roborock Q7 L5 is a great purchase.
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Reviewed in the United States on December 1, 2025
★★★★★ 5
Strong Vacuum Performance, Weak Mop Function
Color: Black01
The Roborock Q7 L5 delivers strong vacuum performance. The suction is powerful and picks up pet hair, dust, and debris with ease. Floors look clean after each run, and the dual anti‑tangle system helps keep the brush clear even in homes with heavy shedding.
Navigation is smooth and efficient. It moves around furniture accurately, avoids obstacles well, and returns to the dock reliably when it needs to recharge.
The mopping feature is quiet, which is a nice benefit. It operates with very low noise, but the cleaning action is minimal. The mop pad mostly drags behind the unit and offers only a light wipe, so it doesn’t replace a real mop.
The vacuum itself is louder, which is expected from a machine with strong suction. It offers different suction levels, so you can adjust the noise and power depending on the room or flooring.
What stands out:
Excellent suction power
Great at picking up pet hair
Smart obstacle avoidance
Quiet mop function
Multiple suction levels
Reliable self‑charging
What could improve:
Mop function is weak
Vacuum noise increases at higher suction levels
Overall, this is an excellent vacuum with strong cleaning performance and smart features. If vacuuming is your priority, it’s a great choice. The mop is more of a bonus than a true cleaning tool.
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Reviewed in the United States on January 23, 2026