I have recently tried to retrofit an existing overhead crane with a 8 channel 433mhz 12 v relay module with a receiver and a transmitter I bought online. My existing crane already has a button pendant for controlling the movement which works fine. My objective is to make the controls for the overhead crane wireless. I am using the 12v relays from the module to provide 110 v ac to 3 phase contactors powering the crane motors for up/down, cross travel and long travel. The overhead crane works fine with no load. However, whenever I lift a heavy load, the controls go awry. For example, when I press the wireless button for long travel, both long travel and cross travel get triggered. However, this problem doesn't happen if I use the existing crane pendant which is connected in parallel. Can anyone guide me what am I doing wrong? Below is a pic of the relay module.

8 channel 433 mhz relay module

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    \$\begingroup\$ There isn't enough information to solve this. a WAG would be that under load the motors/cables are radiating and interfering with the receiver's proper operation. \$\endgroup\$
    – Aaron
    Apr 18, 2022 at 14:26
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    \$\begingroup\$ You probably mean MHz not mHz. \$\endgroup\$ Apr 18, 2022 at 14:46
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    \$\begingroup\$ @naveen please don't do this! You're possibly already seeing the problems with this ebay board. What happens when one of those cheap relays gets its contacts welded closed, the crane doesn't stop and kills someone? Do you have the necessary professional registration, qualifications and insurance to keep you out of prison or financial ruin? For a crane the only safe solution is to ask the manufacturer for a wireless pendent controller. \$\endgroup\$
    – tomnexus
    Apr 18, 2022 at 14:50
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    \$\begingroup\$ Surely you're not allowed to modify an industrial construction crane with hobby electronics components... This seems ridiculous. \$\endgroup\$
    – JYelton
    Apr 18, 2022 at 15:00
  • \$\begingroup\$ I have extensive experience of overhead crane control systems. At least in Europe, you are absolutely not allowed to place anything on the crane which does not conform to the Machinery Directive - specifically to EN 60204-32. At least the crane switch/machine stop is a safety function. Also there's the Radio Equipment Directive and EN 300 220. At a glance, none of these toys look compliant. \$\endgroup\$
    – Lundin
    Apr 20, 2022 at 13:41

1 Answer 1


You’re trying to use bottom-of-the-barrel hobbyist grade components in an industrial application that demands way more robustness and reliability. You shouldn’t be doing that at all.

There are two viable ways out that I see:

  1. If you have the know-how to improve the performance of those cheap subcomponents, by designing shielding, filtering, etc. – then do so. This makes sense if your time is free or very cheap, or if this retrofit is going to be sold as an off the shelf solution, ie. as a serially made product.

  2. If you don’t have the time or know-how to fix it – and the fix may be non-trivial – then use industrial-grade wireless controls. They will typically perform well without much ado, as long as you follow the installation manual. If there’s no installation manual or a comparable document, then it’s a good indication that the product you’re using is not designed for mainstream industrial market. Why? Because regulatory requirements call for suitable manuals.

  • \$\begingroup\$ The main issue here is that the controller has no suitable way to stop the crane. Industrial remote controls are equipped with a rugged stop switch and typically also a supervised safety relay solution, pretty much with the same safety concerns as an industrial emergency stop. \$\endgroup\$
    – Lundin
    Apr 20, 2022 at 14:00
  • \$\begingroup\$ I think this attempt is made in circumstances where safety isn’t even a secondary concern, but maybe tertiary or quaternary :( You have an excellent point of course. I just hope nobody loses life or limb because of this kludge. Luck will be involved, even if it definitely shouldn’t be – it should be safe by design, not by lucky stars… \$\endgroup\$ Apr 20, 2022 at 21:24
  • \$\begingroup\$ In most countries all cranes need to be inspected on regular basis though. Unless you put one up in your private garage or something, I guess... \$\endgroup\$
    – Lundin
    Apr 21, 2022 at 6:36

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