From: firstname.lastname@example.org (N. Thornton)
Subject: Re: How to make/solder a circuit fast?
Date: 21 Sep 2002 16:42:25 -0700
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <3D85221F.5D187DCE@texas.net> <firstname.lastname@example.org> <3D864834.email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 21 Sep 2002 23:42:26 GMT
firstname.lastname@example.org (The little lost angel) wrote in message news:<email@example.com>...
> On 20 Sep 2002 19:40:43 -0700, firstname.lastname@example.org (N. Thornton) wrote:
> >But you need to know what kind of supply your fan is getting before
> >you do anything. You need to investigate that. If its PWM and you dont
> >pick it up you may have a whole lot of failures.
> Okay, my first run on one of them have not failed for a couple of days
> already. Since I also note the presence of a TO-92 IC on the fan
> supply, can I safely assume even if the PSU was supplying PWM to the
> fan supply PCB, the regulator would have turned it into regular DC
Not really. In a PWM fan drive, the fan will receive the chopped
voltage, no smoothing. If you can see the type number on the IC...
that may help.
So no scope. Do you not have a piezo bleeper? theyre only 20 cents,
they make horrid bleeping noises in lots of things these days, so
they're not hard to find lying about. They're very handy for seeing
whats going on in circuits.
PC scopes are free, as are very old PCs that will run the software. A
486 and an old ISA sound card is all thats needed, with Win 95 or 3.1.
95 needs 12M RAM.
Another way to distinguish is to see if theres a differnce between
average fan supply V and peak V. A moving coil meter will give you
average V. A 1k R then a diode supplying a 1uF capacitor wouild give
you the peak voltage, which can be measured wi digital or moving coil
With a dc supply, peak V will be 0.6v below average, due to the
diode's V drop. With PWM supply, ie a chopped dc supply, Vpeak should
be around 12v, V ave maybe 6v.
You can just take your chances of course, or you can test it.
_ _ _ _____ ________ ______
PWM slow speed: |_| |_| |_| |_ fast speed: |_| |_| |_|