dimmer return update, a little OT but thought I would share

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Ok, so after the awful burning up of the dimmer, it took several days  
for the seller to finally agree to take the 3 I originally ordered back  
(1 burned, 2 unused).  Something to keep in mind.  Take a look at seller  
returns.  If they don't say "30 day free returns" for their policy, look  
for someone else!  At least regarding items like this.  This guy had  
returns but seller pays shipping, which I adamantly refused.  It took  
several days of standing firm once I opened a case along with photos of  
the insides of the burned dimmer with a final threat that I would get my  
money back on the date eBay was allowed to "step in."  That date would  
have been this coming Friday.  The seller finally agreed.  Looks like  
he's Chinese because he must have asked multiple times if I wanted to  
get it repaired or was I sure I didn't want a new one.  NO, I want to  
return them all for full refund and you pay shipping because they are  
not as described and I consider them unsafe.  After plugging in shipping  
estimates today, I can see why he was so concerned.  He sent them in a  
cushioned bag, but not taking any chances in case he claims damaged upon  
return, I was going to return them in a fairly large box... at a cost of  
more than $50 US.  Wow!  Not sure what's happened and I guess I have  
been out of selling for a while now, but never expected a rate like  
that!  So, I will reuse his bag, send insured, keep records and  
screenshots of everything and he will pay it all.  If not, I will have  
all records for eBay if/when the time comes.  All this because seller  
didn't have "free 30 day returns".  By the way, sending them back in his  
bag will cost $16.90 insured.

I had a Chinese power supply arrive DOA a month ago.  Seller had "free  
30 day returns."  I started the return process and within a few hours  
was the Paypal refund.  Before the refund, I had received the link for  
the shipping label.  When sellers are refunding before you send back the  
item, are you still supposed to send it back with the prepaid shipping  
label, or not?  Up to now, I have sent them back.

Just some info you may find useful... or not.

Re: dimmer return update, a little OT but thought I would share
More important than anything else you might do would be to leave direct and honest feedback. This may, possibly, help the next potential victim (oops, buyer, that is).  

Friends do not let friends buy from China (when there is any possible alternative).  

Peter Wieck
Melrose Park, PA

Re: dimmer return update, a little OT but thought I would share
On 11/25/20 11:22 AM, Peter W. wrote:
Quoted text here. Click to load it

I am considering it and it would be the first time, in the 25 years I  
have been registered on eBay, that I left a negative feedback.  Really,  
this seller should have not haggled on this and refunded immediately  
especially after I submitted the pictures.  Not being set up in the  
correct way, however, meant that he can't even have a prepaid label made.

Re: dimmer return update, a little OT but thought I would share
 Chuck wrote:
============

Quoted text here. Click to load it

** Pics of the damage you caused by stupidity ?  

You have been less than honest about what you were *really* doing all along.  

What  PSU  was used ??  
What LED lights ?  
Did you make a wiring error ?

You sound like an expert at blame shifting.  


 .....  Phil  

Re: dimmer return update, a little OT but thought I would share
On 11/25/20 3:30 PM, Phil Allison wrote:
Quoted text here. Click to load it

Uh, excuse me, but I have already made myself quite clear and won't  
elaborate further.  If you doubt, then order one and have a load drawing  
  13.8 VDC at 7 A from a linear supply and see what happens in a few  
hours.  You said before that the 12-24 V was missing information.  Who  
would ever know that it is only a 12V device because that's not what  
they advertise.  In addition to no heatsinking.  I think I've been  
clear.  I thought you were helping, but now I question YOUR motives.

Re: dimmer return update, a little OT but thought I would share
 Chuck the Troll puked:
==================

Quoted text here. Click to load it

**  So now you post two, great big lies.  
   Now I know you are hiding the truth.  

   Thanks for removing all doubt.  

Quoted text here. Click to load it

** Not what I wrote at all -  liar.  

Quoted text here. Click to load it

**  That is nothing like what I wrote !!.  
  -------------------------------------------------------

You are one pig ignorant ass aren't you ?  


.....  Phil  

Re: dimmer return update, a little OT but thought I would share
Chuck:

In short order, you will learn several things about the drongo from down-under:

a) The sun shines from its fundament, and only from its fundament. Whatever else you might see is only a poor substitute for the sun, so do not be mistaken!  
b) Were it to behave face-to-face as it does here, it would be dead. Australians are not anywhere near as tolerant as Brits or Americans of that sort of idiocy.
c) It is on very powerful meds. When it takes them properly, it is not a half-bad tech. When it does not, it remains a not-half-bad tech, but all you will see is that other half.  

In general, it is best ignored.  

Re: dimmer return update, a little OT but thought I would share
On 11/26/20 7:33 AM, Peter W. wrote:
Quoted text here. Click to load it

Took me by surprise, started off good and then, bam, about face, day to  
night, whatever.  I'd hate to be his neighbor, family, or even his pet!  
In any case, I'll no longer see his posts after his tirade.


Re: dimmer return update, a little OT but thought I would share
 Chuck wrote:
============

Quoted text here. Click to load it

---------------------------------------------------------------------------------------------
 **  FYI  Mr Shithead:  

Peter Weike is a vile, raving lunatic and a public menace on usenet.  

The geriatric fool is actually is a jumped up radio ham with mental issues and a huge dose of ASD or autism.  

I  *was* happy to assist you till I realised you were a dishonest little shit scamming you way through life.  

Have a rotten day.  


...... Phil  





Re: dimmer return update, a little OT but thought I would share
On that note, every day is a rotten day for the drongo from down-under. It has my sympathy, but not my respect.  

Re: dimmer return update, a little OT but thought I would share
On 11/27/20 7:24 AM, Peter W. wrote:
Quoted text here. Click to load it

Looks like he must have responded to my comment since you responded.  Do  
yourself a favor (maybe?) and plonk him like I did.  No point in  
introducing more craziness into a world that is already crazy enough!

Re: dimmer return update, a little OT but thought I would share
Quoted text here. Click to load it

If you check the headers, you'll see that Peter W. uses google groups  
to post -- which means he has no killfile capability and can't have his  
newsreader hide his postings.


Re: dimmer return update, a little OT but thought I would share
On Fri, 27 Nov 2020 20:21:21 +0000 (UTC), Don't Feed The Troll

Quoted text here. Click to load it

My Google Filter   Message-ID:googlegroups.com


KenW

Re: dimmer return update, a little OT but thought I would share
 Chuck wrote:

==================

Get off this NG -  or I will make you.  


......... love,   Phil  


Re: dimmer return update, a little OT but thought I would share
Quoted text here. Click to load it

One, you can't -- Usenet does not give you that power.

Two, Chuck has killfiled you, so he will not see any of your outbursts  
again.  That's what the "plonk"  
(https://www.urbandictionary.com/define.php?term=plonk ) means.

Chuck is able to killfile you because unlike you, who is using that  
awful google groups web UI, he uses a real newsreader and so he can add  
you to a list (the killfile) in his newsreader to have it automatically  
ignore your rants.



Re: dimmer return update, a little OT but thought I would share
Some things to keep in mind.

The Drongo from down-under is:

a) Alone.
b) Owns nothing other than what is on its back and a few accessories thereto.  
c) Neither friends, nor family, nor pets.  
d) Only those neighbors that perforce share the flat complex in which it squats.  
e) Is very likely older than I am - and therefore there no prospects of anything ever getting any better for it.  

As previously noted - a creature to be pitied - not one due any respect.  

Peter Wieck
Melrose Park, PA  

Re: dimmer return update, a little OT but thought I would share
 Peter W. is a Vile POS LIAR wrote:
---------------------------------------------------

** Peter Weike is a vile, raving lunatic and a public menace on usenet.

The geriatric fuckhead is actually a  *jumped up radio ham* with mental issues and a huge dose of ASD or autism.

But he is not to be pitied for his condition.  

 He is to be despised.  



.....  Phil  


Re: dimmer return update, a little OT but thought I would share
On 11/27/20 4:57 PM, Phil Allison wrote:
Quoted text here. Click to load it

This should be interesting to watch.


--  
"I am a river to my people."
Jeff-1.0
We've slightly trimmed the long signature. Click to see the full one.
Re: dimmer return update, a little OT but thought I would share
Quoted text here. Click to load it

You are clearly confused.  NE555 that you mention clearly shows
that chinese unit is a switching one.  Quality switching unit
would contan inductor, but with slow elements like LM358 and
NE555 switching freqency must be rather low, so one would
need big (read expensive) inductor.  So you probably have
plain PWM unit.  Such unit is fit only for driving LED-s
that have integrated resistors (most consumer lights seem be
like that) and which are (at least approxiatly) matched to
your power supply.  That is 12V LED still needs 12V supply.
If you used 12V LED with 13.8V supply, then you get much
higher current than expected.

Concerning design, with 2 mosfets in parallel switched
fully on you expect resonably current sharing, so
nominally 15A per mosfet.  With nominal Rdson of 0.006 Ohm,
we get 0.006*15^2 = 1.35 W per mosfet.  However, at that
power mosfet will get hot and Rdson will grow, say double
(when junction temperature is 175C).  Then we get 2.7W,
which is too much for TO-220 without a heatsink.  Howewer,
at 12A per mosfet we get 1.78W, which gives some margin
for unequal current sharing.  So, 30A is short term
rating, 24A (that is 12*2) is reasonable max.  For reliable
long term operation I would prefer better margin.  I would say
that 10A is quite conservative.  Above was assuming unit
fully on.  When duty cycle is less than 1, power loss is
proportionally reduced, so we have less heat.

Concerning voltage, LM358 and LM7805 are rated for
30V, so no problem here.  Mosftes have 70V rating,
also OK.  NE555 has lower rating, but presumably it
is supplied by LM7805 so no problem with overvoltage
here.

In info you gave the only suspiciuos part is 7805
regulator.  Namely, we need some voltage to control
gates of mosfets.  5V is too low (Rdson would increase).
8V would be enough and 7808 could easily make it
from 12V input so 7808 would be more natural.  There
are other possible sources of gate control voltage,
but if circuit uses 5V then maximal current would be
reduced (10A still should be OK).

When LED is for lower voltage then your supplay, then
you can use PWM circuit as long as peak current
trough PWM circuit is limited (by LED and supply)
to safe value (say 24A), but clearly this lowers
possible power of LED much more than decrease in
voltage would suggest.  Current trough LED grows
quickly with voltage, so nominal current of LED
at its nominal voltage must be much smaller than
24A to make sure that it will not increase 24A
at increased supply voltage.

Now, what went wrong?  Some possibilies are:
1) units were defective, possible but IME quite rare
   with chinese selers
2) design error like too low gate voltage or too
   limited heat dissipation trough case
3) your 13.8V coused much larger peak current,
4) your LED has some electronics inside including
   nontrivial filtering capactior(s), in such case
   you can get fairly large peak current
5) very high ambient temperature
6) other like surge, short in load etc...

Now, except for 1, 4 and 6 it looks unlikely that other
reasons alone would cause failure because at nominal
8.5 there is considerable safety margin, but combination
of them together may be enough.

Anyway, I would expect good seller to have clear instruction
with warning that power supply should be matched to
LED-s.

--  
                              Waldek Hebisch

Re: dimmer return update, a little OT but thought I would share
Quoted text here. Click to load it

I think that's the fair and honorable thing to do... you're honoring
the terms of the refund offer, as the seller is trusting you to do.
Not sending back the product would be a violation of that trust (and
the contract of the sale).

The exception would be if the seller tells you that there's no need to
return the bad unit.  I've had this happen occasionally, when the unit
in question was either irreparably damaged in shipment (the package
must have gotten caught in a transport-belt gearbox) or where it was
probably not economically feasible to repair it (a replacement battery
for a cellphone which apparently had a bad control chip and wasn't
"seen" by the phone).  The battery vendor just asked that I dispose of
the dead unit properly via an e-waste collection, rather than throwing
it into the trash.


Site Timeline