Terrible RC Transmitter Made Less Terrible

It should probably go without saying that we’ve got nothing against the occasional bout of elaborate troubleshooting and repair, in fact it’s one of the most common things we cover here. As it turns out, people aren’t overly fond of being fleeced, and there are a lot of smart people out there who will put a lot of work in to keep from having to toss a favorite piece of gear into the trash. We can’t fault them for that.

But we have to say, we generally don’t see those kind of elaborate repairs for something brand new. Unfortunately, that’s exactly what [Marek Baczynski] had to do when trying to review the new iRangeX transmitter for his YouTube channel “dronelab”. He found a transmitter that was so poorly designed and constructed that he had to address a laundry list of issues to make the thing halfway tolerable. As you might expect, he’s not suggesting anyone go run and pick this one up.

The biggest problem is a fundamental flaw with how the gimbals are constructed. Due to poorly mated surfaces between the potentiometer and the stick itself, the accuracy of the controller is very low. The potentiometers don’t even return to zero when the sticks are released. Some tape was used to tighten up the connection and make the controller usable, but such poor tolerances are hard to forgive when accurate control is essentially the whole point of the device.

The other issues took a bit more debugging to figure out. The TX made an absolutely terrible screeching sound when turned on, but [Marek] was sure he was hearing a little bit of melody under the din. Putting the signal through the oscilloscope, he was able to confirm his suspicions. As it turns out, the buzzer used in the TX has a built in tone generator that was overriding the intended melody. Switching it out for a basic buzzer fixed the issue. Similarly, an issue where the radio wouldn’t turn on if it was recently turned off was tracked back to a resistor of the wrong value. Putting a higher lower value resistor in its place sorted that out as well.

It’s hard to imagine how this device made it out of the factory with so many wrong or unsuitable components, but here we are. Not that this would be acceptable at any price point, but as [Marek] points out in the video, it isn’t as if this radio is even all that cheap. For nearly $90 USD, it doesn’t seem unreasonable to expect something that actually works.

This isn’t the first time he’s put “cheap” RC hardware through the wringer. We recently covered his efforts to quantify latency in different transmitters. As the RC transmitter world gets increasingly competitive, detailed analysis like these help separate the real gear from the toys.

32 thoughts on “Terrible RC Transmitter Made Less Terrible

  1. Pushing a certain percentage of faulty units is very common, because the company that ordered them from the Chinese factory has to order more units to replace those that don’t work.

    So some units are made with rejected parts, counterfeit parts, or just substituting parts because the factory didn’t buy or make enough extra parts to fill the quota. Quality control is suspended until the customer complains and demands it.

    1. Or, it might be the same thing as how, year after year, the average laptop breaks down in four years – they don’t get better – and the manufacturers that make them simply switch models so the bad word about breaking laptops wouldn’t affect future sales.

      So someone says “Don’t buy XYZ it’ll just break down”, but there is no XYZ on the market anymore. Now it’s ZWY and nobody knows whether -that- model is any good, and so the manufacturers can keep on pushing substandard hardware year after year.

      1. This is getting worse too.

        I’m seeing tools and components that are obviously coming down the same chute sold under dozens or hundreds of names to try and spoof online cost/quality comparisons. The system has gotten so noisy that quality products that should be easy to find are obscured or may disappear completely.

        1. Do you remember excelent HP test instruments? Er, I mean Agilent… Wait, now is Keysight. Or IBM.., hmmm, ok, ok, Lenovo. Farnell? Nooo E14… etc.etc.

          I think that these kind of guys were who invented and massively exploited the trademark blockchain long before bitcoin.

      2. This is why I just won’t spend good money on a laptop. It amazes me to see how so many people are forgoing desktop computers entirely and only own a laptop. I get the idea of taking less space and being portable but… they suck! And if you keep replacing them every time they break they suck your wallet dry!

        Instead I prefer to have a good solid desktop with an always-on internet connection. If I want to be portable I can connect to it remotely through my phone. For a bigger screen I can use a cheap tablet or even an old, severely outdated but inexpensive and higher quality laptop tethered to my phone.

        To allow for this I used to leave my desktop turned on all the time. Being more power conscious now I just ssh into my NAS and use it to send a wake on lan packed to the desktop when I need it. If I didn’t have the NAS I could probably set up ssh access to my router and use that.

      1. but what if this purchase and fixing is now done by others via this article/fixing/guidance? imagine now that 20 people go on to fix the poor quality item and in the process, there’s some electronics learning involved and inspiration propagated. and financial savings.

        1. Cheating sellers will be more than happy if everybody did that. That is why when I get blatantly fake or defective products clearly with zero QC or just no product at all always demand a refund, and so far so good.

          Even if it’s just $0.5 and won’t worth one minute of your time at least they won’t get free money cheating and may help to discourage them or if are just marketers at least pay more care and complain themselves to the manufacturer and not only the bad feedback.

          Over the past couple of years have a sample of several hundreds and a 5-20% cheat/defect rate depending of kind of product is just…well cheating by design and seems getting worse. I suspect that all those lots of new sellers with stores a few months old who not only send fakes but ship out only 80% of orders while providing fake tracking numbers are money laundering somehow. And Aliexpress is specially bad for that because your feedback warning unsuspecting fellow victims won’t show up until a month later or two/three after the order was placed. Plenty of time to hit and run.

          Anyways usually end up spending several hours trying to fix the damn thing instead of just throwing it away as they should have done in the first place because rarely is worth it other than for the fun/frustration of tinkering.

          1. yeah, that’s definitely a better point of view than what i suggested. and i agree with most of it. i often wonder how new (ebay) Sellers clone their offerings (10,000+ items) but maybe it’s just the names/entities change. my experience, as far as new goods go, is with cheap junk under $5 — some of it i don’t bother to use or find out if it’s junk or not. if mass quantity or higher-priced stuff is broken by design or manufacture, i certainly would be furious and possibly seek refund/exchange. there’s one point which i wish were more often realized: a lot of goods would not be affordable ot exist if it weren’t for the shady deals and poor quality of other items. each time someone mentions ‘Chinese’ in relation to these electronics/components, i’m thankful for the cheapness both moneywise and qualitywise.

          2. >”a lot of goods would not be affordable ot exist if it weren’t for the shady deals and poor quality of other items”

            The only person you’re cheating there is yourself. These low quality imports represent a loss of money from the economy, so while you may score a nice find on the cheap, lots of other people waste their money on junk, and all are increasing the trade deficit which is putting local businesses out of work and increasing unemployment and poverty.

            Lots of good stuff can be made on the cheap, but lots of bad stuff can be made even cheaper, and the bad stuff ends up costing you more in the long run.

          3. Here’s how it works.

            Local prices by local workers may be $10 per item, but that money goes in circles inside the local economy and while the price is high, so are the wages, and everyone can afford the prices.

            Then comes the junk imports, and people start buying $5 items because they’re cheaper. Now the money goes out of the economy and sooner or later the local businesses scale down and the wages drop, people are put out of jobs, and now anyone can barely afford the $5 prices.

            Adding insult to injury, the $5 item isn’t even half as good as the $10 item, it’s less than 1/4 as good on average thanks to all the cheaters who push absolute garbage on the market, so the average person ends up paying $20 for the same utility they used to get for $10 while their wages can only support paying $5.

          4. Point in case: chinesium shoes.

            It used to be that you could buy decent shoes for about $50-75 and $20 would buy you plastic imitations that would last you maybe couple years. I’m not talking old prices, but what a cheap shoe then would cost today.

            These days the $50-75 shoes are plastic imitations, and the $20 shoes are literally made out of paper and cardboard soaked in some sort of rubber. They’re not even sown together, they’re glued, and there’s a small strip of steel sunk into the sole to keep a semblance of rigidity; possibly the most expensive part of the shoe. I bought a pair of walkers last June, and they split in half across the middle by the end of October.

            The last time people had to buy shoes made out of paper was during wartime rationing.

          5. @S – Without cheap, low quality goods I don’t think our hobby could exist. Think of our tools. If only good, high quality tools existed.. and at the price those go for how many of us would ever even learn to solder?

            i think there comes a point when a price is low enough that it should be obvious to the consumer that it is either a a project to be improved upon or just trash. Need an example, how about K40 Laser engravers. I intend to get one and fully expect to need to repair and upgrade it right away. But… if it weren’t available.. the alternative would be I get no laser at all!

        2. @knowmore

          If this were an inexpensive item I’d be right there with you on that. I don’t think 100s of Hack a Day readers should go out and buy a $90 item that needs a bunch of waranty voiding work done to it just because they have now been shown how to.

  2. I’m curious to learn how you traced the 1-minute wait before turn-on period to “something that looks like a brown-out detection circuit”. I would like to know how you determined what resistor was improperly sized and then what size to make it to fix the problem. An easy fix, yes, but getting there suggests a knowledge of R/C reverse engineering that the average electronics tech doesn’t possess. It would take me days to figure it out, especially without a schematic. Can you share with us your methodology on that? Thanks.

    1. Welcome to the world of reverse engineering :D

      There is a nice view of that part of the board at 02:53 in the video so you can look at that while reading on. We traced the power line from the battery connector, labeled P1, to a P-MOS labeled Q3. Its output is labeled “Power 1” so it looks like it’s the main power line of the board, and that MOSFET is controlling it. The gate of that transistor is controlled by the small analog circuit above it.

      We guessed that this circuit is to prevent the battery from being over-drained if you leave the switch in the “on” position, but the battery is too low to actually run the device. Without such a circuit a device will start switching off and on frantically, while murdering the battery. There needs to be some sort of a “latching” mechanic in that circuit.
      There are only 2-3 caps there, so we just measured them all when the device is on, off and during transitions. One of them would slowly discharge after being turned off – C21 – and is driving a latching transistor, Q5. We forced it empty with a pair of tweezers and bingo – the device restarted correctly. The resistor next to that cap – R21 – is what is causing it to discharge, so a lower resistance makes it discharge faster.

      Ideally we would replace the cap with a smaller capacitance, and THAT is likely the real mistake in the design. It looks like they simply used the same capacitor as is used nearby – C01. Re-using the same part saves you a slot on the automatic pick-and-place assembly machines, so there is a good reason to try and do that where possible. 99% of the time caps are used to store energy, and putting a bigger one is not detrimental to the device. This is that 1%. It probably should have been a 10uF or 22uF one.

      1. Ditto on the nice explanation.
        My thoughts ran to the 555 and the resistor & capacitor, timing circuit that I once used as a power on~speaker thump delay that I needed for an ancient installation of car audio.
        The power behavior of the transmitter is the giveaway as to the presence of said circuit.

  3. heh i also have an RC transmitter that never worked, and i have not thrown it out because someday i figured i would repair it. but that was years ago and since i’ve had kids i never fly anymore so it has languished :(

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