X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com X-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=PqFBS9n4etjFV9So9hbcEWQzjNzy1+cX+GYQ4v/jMss=; b=asNJ+1MSbKuRJcvDHori3884KPK4Km/hX+Vl0TKQVaHs6W+o27Myd43iVyk74JRkD+ R25u/SX/NT9WAcBgEiE7OzwknShkyBBeKD2lrXVjls8rz4kynq8Tk3c5OqLSvsJC9mO4 NwILhzWeU64KAjNyhBh72+W/GeEP5WbIyZ6lsDDdw173k4uLSRSccNobPl3YaFmMHE78 MaML9A2aYKFZWhNqpHmNxgCiGEBge9YS57iiMouO4c/ydzriVPbi196R+bMz3fQxnCHv r+se8QcTersuEoXBVWAm0oqhk2PctZgTv+jqcP7jUpsgZURfvnXyMCnVKeCA7R+gX3L6 clGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=PqFBS9n4etjFV9So9hbcEWQzjNzy1+cX+GYQ4v/jMss=; b=N5I6tvjnjOXoFmhJimKcpCwCETIu4GNQMY7Os2p4uy3sq5jdH4OPPcs38Z/2fjvllf Z5wKE+WZOR7diooJGSMDnPbn1hpD7NdYHN7bfxgITXFllDX3rEoIL4KrTvflq8j0v/A3 SjQ47XifMu+GvhfB8kNXboi6eCMxBTljdxIjgj9Tcs3IG7w+m49+lbrdWAh6vK8h/uVl 1LnLLu7EwB9x/j+GkyVsyC10YUqUgoOdqxybEHYsrt39mdkO6fopidvnUCpnujVkfSsb nZwJp7E8FvlDvRhOV22innhAvCR1io/bdRFflOLgz7ypzpF9ra/vv85CGdrrYiO2Tc3N Q6jA== X-Gm-Message-State: AA+aEWbGSScB1lVRzZohzfdm46vuB9bzO0AYY7nhm8XhyXK+3ylwNWCh cq0yR23hLvlJQAbCoTKweU/g3osT2cPkTB+5k03d+aVa X-Google-Smtp-Source: AFSGD/Wrc4CyN6tqEVGd0scCGJZHzW2JxQCdT2v3KvW7mXhnt8IoUIpLyk+UkclOCktRnob/WVxNYG4GgNf5K0+kPhs= X-Received: by 2002:a9d:4c88:: with SMTP id m8mr19276103otf.360.1543334079361; Tue, 27 Nov 2018 07:54:39 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <7c1717bb-1b7d-360f-d06a-71ee6983eea1 AT linetec DOT nl> From: "Luis de Arquer (ldearquer AT gmail DOT com) [via geda-user AT delorie DOT com]" Date: Tue, 27 Nov 2018 16:54:38 +0100 Message-ID: Subject: Re: [geda-user] [off-topic] 24V automotive (truck) design issues To: geda-user AT delorie DOT com Content-Type: text/plain; charset="UTF-8" Reply-To: geda-user AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: geda-user AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk Hi Richard, On car, we normally use a TVS with a high enough value so that supressed load dump doesn't affect it, yet the other pulses can be drained through -so 36V to 40V. 33V TVS showed to burn on load dumps. Anyway, let us know what you find out! I am curious to see why it failed :) Luis 2018-11-27 11:59 GMT+01:00, Richard Rasker (rasker AT linetec DOT nl) [via geda-user AT delorie DOT com] : > Hi Luis, > > Op 26-11-18 om 23:06 schreef Luis de Arquer (ldearquer AT gmail DOT com) [via > geda-user AT delorie DOT com]: >> Hi Richard, >> >> There are quite a few spikes that can damage electronics on the >> truck. You can find most of them on ISO 7637 (second part has the >> pulses definition). > > Thanks, I, er 'found' a copy of this, and the worst I see, are > negative-going 1ms-pulses to -600 volts @ 50 ohms for 24V systems. > > Then again, the TVS diode I used (SMAJ33CA) should handle this just fine. > >> The worst I can remember for car is -150V for 2ms >> approx, surely more on trucks. Positive pulses of over 100V happen >> often when parallel inductive loads are disconnected (such as windows, >> etc), but this are normally under 100us. >> >> Load dump is fairly unusual though, since that requires the battery to >> be removed from the truck while alternator is running. Its strength >> depends on whether the truck has load dump supressor or not (cars now >> normally have it, but I don't know trucks...). With load suppresor, >> you may see about 58V for up to 300-400ms. It is currently defined in >> ISO 16750-2 (2012 or later). > > For 24V systems, I see load dump peaks up to 200 volts for 350 ms at > only a few ohms -- this would definitely fry the TVS diode I used and > everything behind it. I guess I'll have to employ either a far more > rugged TVS diode or an overvoltage disconnect circuit to handle this. > > But as you say, this occurrence (battery disconnect with running > alternator) should happen only on rare occasions, so it doesn't explain > two failures within a week. > > AFAICS, all the other pulses should be no real problem for the TVS diode > (I used this simple setup several times with normal 12V cars, and never > had any trouble). > >> This may help: >> - Try to get the boards that failed for analysis. Did the TVS fail? > I'll see tomorrow, when the boards arrive. >> - Revise all input capacitors voltage ratings >> - It can help having a high voltage series diode at the input such as >> BAV21W, followed by a tanky 220uF or higher capacitor: This should get >> rid of most pulses, except load dump. > > Unfortunately, there is no room on the PCB itself for a hefty capacitor > on the input (as it would need to have a working voltage of 200 volts > for load dump handling), but I don't think that's necessary in case of a > disconnect solution. It's a non-essential gadget, and it's no problem if > it cuts out for a fraction of a second on rare occasions. > >> - For load dump, you really need to know if there is a supressor or >> not. The difference is huge. > > I think that I simply will have to take the worst case scenario. These > people have no (haha) truck with conditional reliability; things should > 'just work, period'. > > Anyway, thanks for your elaborate reply! > > Best regards, > > Richard Rasker >