Homebrew PCBs

On Thu, 02 Oct 2003 01:46:19 -0000, Steve <alienrelics@...> wrote:

> --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
> <stefan_trethan@g...> wrote:
>> What you describe there is a simple membrane pump.
>> thousands sold each year (a lot of them for air pumping).
>> i tried it with a speaker @50hz, speaker diameter about 12cm.
>> the membrane hat to be sealed (used silicone).
>> with air id did make some suction (wanted it for vacuum-bag lamination).
>> but not very much, very low efficiency. (@50hz)
>> (membrane pp amplitude was 5mm  - then it smoked, stopped to move and i 
>> discarded it ;-))
>
> Phew, I don't feel so bad then.
>
> I wouldn't expect a diaphram style pump to be very good at pulling a
> vacuum.
>
> Steve


they are used for desoldering vacuum pumps (the pistol type with a tip with 
a hole).
(for desoldering about 5cm diameter and 50hz frequency (maybe 100), no idea 
which amplitude)
also for smd vacuum holding i have seen a membrane pump.

it is not a bad concept - cheap, no parts to be sealed..
but i think it may be because of the weight, thus the resonant frequency, 
why i have never seen one for liquid. let me know if anyone has.

the speaker pump i built would have been enough for smd holding. membrane 
pumps are cheap to get for aquarium air agitation.

but if you ever need a good cheap vacuum/compressed air pump get a used 
fridge compressor.
run it some time to remove most oil and for pressure air build a dry filter 
(paper towels or cloth)
to filter oil mist.
if you want to use the vacuum side you need to add a valve, from powering 
the pump until vacuum is
formed it takes some time (not so with pressure, this is almost instant).

this can be a very nice vacuum generator for the desoldering iron (if you 
add a valve to the handle).

(it is no high vacuum generator for evaporating a electron microscope! no 
idea how many mmHg
but i testet it with water and 3 meters were no problem (the room was only 
3 meter...))


stefan
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