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Mail Archives: geda-user/2018/11/26/11:57:35

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From: John Doty <jpd AT noqsi DOT com>
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Subject: Re: [geda-user] [off-topic] 24V automotive (truck) design issues
Date: Mon, 26 Nov 2018 11:56:15 -0500
References: <eda2cdce-ccc4-67f4-ccde-6798043e5f41 AT linetec DOT nl>
To: geda-user AT delorie DOT com
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Lots of info out there, google "load dump protection=E2=80=9D.

> On Nov 26, 2018, at 10:58 AM, Richard Rasker (rasker AT linetec DOT nl) [via =
geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
>=20
> Hello,
>=20
> Apologies for this off-topic question, but I found that quite a few =
people here have a lot of expertise in specialized electronics subjects.
>=20
> My issue: I was asked to build a relatively simple LED lighting =
application for use in trucks (24V).
>=20
> I built a handful of prototype boards for testing, based on an =
LMR14206 step-down device (see attachment), and while these work =
perfectly fine on the workbench, even up to 50 volts, I had already two =
failing when testing on an actual truck for several days.
>=20
> I suspect that voltage spikes may be the cause, maybe in conjunction =
with lack of a sufficiently large buffer capacitor on the input. But not =
having much experience in the area of automotive-quality design, I don't =
really know what to expect and how to handle this -- I did use a TVS =
suppressor diode, but perhaps I should take some extra measures, like a =
large cap across the supply input.
>=20
> =46rom what I can find on the Internet, it would appear that the 24V =
supply may have spikes of up to 200 volts, which of course can wreak =
havoc with anything designed for a few dozen volts max.
>=20
> Any thought on this? Or could someone point me to design guidelines, =
or perhaps example schematics of actual electronic devices for =
applications like this? No doubt, there must be pertinent information =
out there, but I have trouble locating it.
>=20
>=20
> Thanks in advance,
>=20
>=20
> Best regards,
>=20
> Richard Rasker
> <GL_MAN_M.png>

John Doty              Noqsi Aerospace, Ltd.
jpd AT noqsi DOT com




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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" =
class=3D"">Lots of info out there, google "load dump protection=E2=80=9D.<=
div class=3D""><br class=3D""><div><blockquote type=3D"cite" =
class=3D""><div class=3D"">On Nov 26, 2018, at 10:58 AM, Richard Rasker =
(<a href=3D"mailto:rasker AT linetec DOT nl" class=3D"">rasker AT linetec DOT nl</a>) =
[via <a href=3D"mailto:geda-user AT delorie DOT com" =
class=3D"">geda-user AT delorie DOT com</a>] &lt;<a =
href=3D"mailto:geda-user AT delorie DOT com" =
class=3D"">geda-user AT delorie DOT com</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div =
class=3D"">Hello,<br class=3D""><br class=3D"">Apologies for this =
off-topic question, but I found that quite a few people here have a lot =
of expertise in specialized electronics subjects.<br class=3D""><br =
class=3D"">My issue: I was asked to build a relatively simple LED =
lighting application for use in trucks (24V).<br class=3D""><br =
class=3D"">I built a handful of prototype boards for testing, based on =
an LMR14206 step-down device (see attachment), and while these work =
perfectly fine on the workbench, even up to 50 volts, I had already two =
failing when testing on an actual truck for several days.<br =
class=3D""><br class=3D"">I suspect that voltage spikes may be the =
cause, maybe in conjunction with lack of a sufficiently large buffer =
capacitor on the input. But not having much experience in the area of =
automotive-quality design, I don't really know what to expect and how to =
handle this -- I did use a TVS suppressor diode, but perhaps I should =
take some extra measures, like a large cap across the supply input.<br =
class=3D""><br class=3D"">=46rom what I can find on the Internet, it =
would appear that the 24V supply may have spikes of up to 200 volts, =
which of course can wreak havoc with anything designed for a few dozen =
volts max.<br class=3D""><br class=3D"">Any thought on this? Or could =
someone point me to design guidelines, or perhaps example schematics of =
actual electronic devices for applications like this? No doubt, there =
must be pertinent information out there, but I have trouble locating =
it.<br class=3D""><br class=3D""><br class=3D"">Thanks in advance,<br =
class=3D""><br class=3D""><br class=3D"">Best regards,<br class=3D""><br =
class=3D"">Richard Rasker<br class=3D""><span =
id=3D"cid:76E609E8-E167-4B04-8DC0-2CDFC3A4D9A4 AT fios-router DOT home">&lt;GL_MA=
N_M.png&gt;</span></div></div></blockquote></div><br class=3D""><div =
class=3D"">
<span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
border-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; =
font-size: 12px; font-style: normal; font-variant-ligatures: normal; =
font-variant-caps: normal; font-variant-east-asian: normal; =
font-variant-position: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; text-indent: 0px; text-transform: none; =
orphans: 2; white-space: normal; widows: 2; word-spacing: 0px;"><div =
style=3D"word-wrap: break-word;" class=3D""><span =
class=3D"Apple-style-span" style=3D"border-collapse: separate; =
border-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; =
font-size: 12px; font-style: normal; font-variant-ligatures: normal; =
font-variant-caps: normal; font-variant-east-asian: normal; =
font-variant-position: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; text-indent: 0px; text-transform: none; =
orphans: 2; white-space: normal; widows: 2; word-spacing: 0px;"><p =
style=3D"margin: 0px;" class=3D""><font face=3D"Helvetica" size=3D"3" =
style=3D"font-style: normal; font-variant-caps: normal; font-weight: =
normal; font-size: 12px; line-height: normal; font-family: Helvetica;" =
class=3D"">John Doty<span class=3D"Apple-converted-space">&nbsp; &nbsp; =
&nbsp; &nbsp; &nbsp;<span =
class=3D"Apple-converted-space">&nbsp;</span><span =
class=3D"Apple-converted-tab">&nbsp; &nbsp;<span =
class=3D"Apple-converted-space">&nbsp;</span></span></span>Noqsi =
Aerospace, Ltd.</font></p><p style=3D"margin: 0px;" class=3D""><a =
href=3D"mailto:jpd AT noqsi DOT com" class=3D"">jpd AT noqsi DOT com</a></p><br =
class=3D"Apple-interchange-newline"></span></div></span><br =
class=3D"Apple-interchange-newline">
</div>
<br class=3D""></div></body></html>=

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