From bigclivedotcom.
Do NOT leave items like this plugged in. There is no overheating protection and it’s possible for a processor crash or fault to continuously energise a heating element surrounded by plastic.
Aside from the astounding simplicity, this unit is actually very functional. It has a very small PCB running a common vacuum pump and simple heating strip composed of fibreglass string with a heating wire spiralled around it.
The PCB inside has quite an unusual power supply that generates a 10.8V supply for the pump and processor that is also referenced directly to mains to allow driving of the triac that switches the heater wire.
Although the unit can monitor the zero crossing point of the mains waveform, I’ve since confirmed that it is firing the heater in a series of pulses to regulate the heat. (I connected a tungsten lamp to the heater output and it pulsed repeatedly during the heating cycle.)
There is no pressure or temperature sensing. It is all done based on time.
The trickiest bit of reverse engineering the control PCB was the odd power supply chip configuration. Especially with it using a traditional transformer approach versus the usual buck regulator found in non isolated supplies like this. I get the feeling that this PCB may have seen a few revisions in its design over time. The control IC used is marked 3773CH but it didn’t match any schematics I found for that number.
I’ve noticed that some eBayers in the UK use vacuum sealers to squish things like beanies down for postage. The Royal Mail has strict size limits with huge price jumps, which makes it very viable to shrink soft things down for shipping.
These are available from many suppliers on eBay and AliExpress. Just search for vacuum sealer.
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