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FITS box

Started by John Larkin October 15, 2021
https://www.dropbox.com/s/w30gguaelu7538o/Fits_Foam_2.jpg?raw=1

Just took a minute on the band saw. Four FITS boxes will fit in that
3U tray.

Now it just needs a little code.

-- 

If a man will begin with certainties, he shall end with doubts, 
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
On Fri, 15 Oct 2021 15:56:20 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

> >https://www.dropbox.com/s/w30gguaelu7538o/Fits_Foam_2.jpg?raw=1 > >Just took a minute on the band saw. Four FITS boxes will fit in that >3U tray. > >Now it just needs a little code.
We'll have over 400 relays in this box. It could get hot. We can play the trick of pulling them in at full coil voltage and then dropping to holding voltage. That will cut power dissipation by at least 4:1, likely more. We were discussing boogering various switching regs to do that, but we don't really need a regulator... just the switching part. This should work: https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 The Ixys driver claims to be very resistant to latchup, so we don't really need the catch diode. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
On a sunny day (Sat, 16 Oct 2021 10:05:29 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<911mmgd22r7tvdtcbi12ka4sgm7trjh8ga@4ax.com>:

>dropping to holding voltage. That will cut power dissipation by at >least 4:1, likely more. > >We were discussing boogering various switching regs to do that, but we >don't really need a regulator... just the switching part. > >This should work: > >https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 > >The Ixys driver claims to be very resistant to latchup, so we don't >really need the catch diode.
You can do the same with 2 NPNs, 1 diode and 2 supply rails, no PWM needed. Maybe RC as delay to switch off the first NPN on the high supply rail.
On Sat, 16 Oct 2021 18:28:02 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>On a sunny day (Sat, 16 Oct 2021 10:05:29 -0700) it happened >jlarkin@highlandsniptechnology.com wrote in ><911mmgd22r7tvdtcbi12ka4sgm7trjh8ga@4ax.com>: > >>dropping to holding voltage. That will cut power dissipation by at >>least 4:1, likely more. >> >>We were discussing boogering various switching regs to do that, but we >>don't really need a regulator... just the switching part. >> >>This should work: >> >>https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 >> >>The Ixys driver claims to be very resistant to latchup, so we don't >>really need the catch diode. > >You can do the same with 2 NPNs, 1 diode and 2 supply rails, no PWM needed. >Maybe RC as delay to switch off the first NPN on the high supply rail. > >
That would work, maybe use a pfet. Or the Ixys and 2 diodes. It does need another main supply. Might be a big deal compared to one SO8 per board. The inductor shouldn't be bad. The 2nd supply rail switcher would need an inductor. The uP can round-robin the four relay boards. Select one, pop it up to 24 volts, bang the relay driver shift register, wait maybe 25 milliseconds, drop the voltage, move on to the next one. Relays have a big pull:drop voltage ratio, but it's not always well specified. 50% is probably conservative, 1/4 power. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
16.10.21 21:15, jlarkin@highlandsniptechnology.com wrote:
>On Sat, 16 Oct 2021 18:28:02 GMT, Jan Panteltje ><pNaonStpealmtje@yahoo.com> wrote: > >>On a sunny day (Sat, 16 Oct 2021 10:05:29 -0700) it happened >>jlarkin@highlandsniptechnology.com wrote in >><911mmgd22r7tvdtcbi12ka4sgm7trjh8ga@4ax.com>: >> >>>dropping to holding voltage. That will cut power dissipation by at >>>least 4:1, likely more. >>> >>>We were discussing boogering various switching regs to do that, but we >>>don't really need a regulator... just the switching part. >>> >>>This should work: >>> >>>https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 >>> >>>The Ixys driver claims to be very resistant to latchup, so we don't >>>really need the catch diode. >> >>You can do the same with 2 NPNs, 1 diode and 2 supply rails, no PWM needed. >>Maybe RC as delay to switch off the first NPN on the high supply rail. >> >> > >That would work, maybe use a pfet. Or the Ixys and 2 diodes. It does >need another main supply. Might be a big deal compared to one SO8 per >board. The inductor shouldn't be bad. The 2nd supply rail switcher >would need an inductor. > >The uP can round-robin the four relay boards. Select one, pop it up to >24 volts, bang the relay driver shift register, wait maybe 25 >milliseconds, drop the voltage, move on to the next one. > >Relays have a big pull:drop voltage ratio, but it's not always well >specified. 50% is probably conservative, 1/4 power. > > >
Often the reduced operation current has limited specs, so no guarantee with vibration and temperature changes (you need to take high ambient temperature into account) -- Klaus
On Sun, 17 Oct 2021 08:18:10 +0200, Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>16.10.21 21:15, jlarkin@highlandsniptechnology.com wrote: >>On Sat, 16 Oct 2021 18:28:02 GMT, Jan Panteltje >><pNaonStpealmtje@yahoo.com> wrote: >> >>>On a sunny day (Sat, 16 Oct 2021 10:05:29 -0700) it happened >>>jlarkin@highlandsniptechnology.com wrote in >>><911mmgd22r7tvdtcbi12ka4sgm7trjh8ga@4ax.com>: >>> >>>>dropping to holding voltage. That will cut power dissipation by at >>>>least 4:1, likely more. >>>> >>>>We were discussing boogering various switching regs to do that, but we >>>>don't really need a regulator... just the switching part. >>>> >>>>This should work: >>>> >>>>https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 >>>> >>>>The Ixys driver claims to be very resistant to latchup, so we don't >>>>really need the catch diode. >>> >>>You can do the same with 2 NPNs, 1 diode and 2 supply rails, no PWM needed. >>>Maybe RC as delay to switch off the first NPN on the high supply rail. >>> >>> >> >>That would work, maybe use a pfet. Or the Ixys and 2 diodes. It does >>need another main supply. Might be a big deal compared to one SO8 per >>board. The inductor shouldn't be bad. The 2nd supply rail switcher >>would need an inductor. >> >>The uP can round-robin the four relay boards. Select one, pop it up to >>24 volts, bang the relay driver shift register, wait maybe 25 >>milliseconds, drop the voltage, move on to the next one. >> >>Relays have a big pull:drop voltage ratio, but it's not always well >>specified. 50% is probably conservative, 1/4 power. >> >> >> >Often the reduced operation current has limited specs, so no guarantee with vibration and temperature changes (you need to take high ambient temperature into account)
The Omron G5Q relays are unusual in that they have a specified hold voltage, 30 or 40% for parts in the family. Under 40 milliwatts hold. Many relays specify a guaranteed dropout voltage, typically 5% of full coil voltage. That doesn't help here. We'll have to test our selected mult-sourced relays. The PWM hold set factor could be in a cal table. High ambient temp is avoided by cutting the coil voltages! I'd rather not have a fan in the box, but it might be necessary. We can impose restrictions on how many relays can be energized at once. Some combinations make no sense. 150 relays on at 40 mW each is only 6 watts, compared to 400 relays at 400 mW = 160 watts. A similar product, made by someone else, gives the users full relay control with no setback, and the manual is full of big-font warnings about frying the box. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
On Saturday, October 16, 2021 at 1:05:38 PM UTC-4, jla...@highlandsniptechnology.com wrote:
> On Fri, 15 Oct 2021 15:56:20 -0700, John Larkin > <jlarkin@highland_atwork_technology.com> wrote: > > > > >https://www.dropbox.com/s/w30gguaelu7538o/Fits_Foam_2.jpg?raw=1 > > > >Just took a minute on the band saw. Four FITS boxes will fit in that > >3U tray. > > > >Now it just needs a little code. > We'll have over 400 relays in this box. It could get hot. > > We can play the trick of pulling them in at full coil voltage and then > dropping to holding voltage. That will cut power dissipation by at > least 4:1, likely more. > > We were discussing boogering various switching regs to do that, but we > don't really need a regulator... just the switching part. > > This should work: > > https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 > > The Ixys driver claims to be very resistant to latchup, so we don't > really need the catch diode.
You don't see that method being used much because the relay loses all of its vibration/g resistance. Just a little bump to the chassis can cause it to drop out. You might want to test this yourself.
> > > > -- > > Father Brown's figure remained quite dark and still; > but in that instant he had lost his head. His head was > always most valuable when he had lost it.
On Sun, 17 Oct 2021 08:51:47 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Saturday, October 16, 2021 at 1:05:38 PM UTC-4, jla...@highlandsniptechnology.com wrote: >> On Fri, 15 Oct 2021 15:56:20 -0700, John Larkin >> <jlarkin@highland_atwork_technology.com> wrote: >> >> > >> >https://www.dropbox.com/s/w30gguaelu7538o/Fits_Foam_2.jpg?raw=1 >> > >> >Just took a minute on the band saw. Four FITS boxes will fit in that >> >3U tray. >> > >> >Now it just needs a little code. >> We'll have over 400 relays in this box. It could get hot. >> >> We can play the trick of pulling them in at full coil voltage and then >> dropping to holding voltage. That will cut power dissipation by at >> least 4:1, likely more. >> >> We were discussing boogering various switching regs to do that, but we >> don't really need a regulator... just the switching part. >> >> This should work: >> >> https://www.dropbox.com/s/ktcerq8uzbi5l5c/Relay_Stepdown.jpg?raw=1 >> >> The Ixys driver claims to be very resistant to latchup, so we don't >> really need the catch diode. > >You don't see that method being used much because the relay loses all of its vibration/g resistance. Just a little bump to the chassis can cause it to drop out. You might want to test this yourself.
Surely not all, and not a little bump at, say, 1/2 coil voltage. The reluctance of the magnetic loop goes way, way up once everything's seated. It would take a big whack to open up the gap much. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.