Well one thing you could do would be to take a voltage measurement at the input to the 7805 regulator.
True that with a light load, the 7805 should run fairly cool. However, the 7805 also runs proportionally hotter the higher the input voltage is. For input voltages down around 11 or 12 volts, it's not running very hot. But go up around 15 volts and over, and that little dickens starts to heat up regardless of the DC load on the 5 volt regulated side. In my applications for the 7805, I always use a massive heatsink usually in the form of a good-size aluminum plate. My earliest nixie clock uses the .25 inch thick x 8 inch x 10 inch aluminum base plate as the 7805 heatsink. The 7805 runs cool on that big plate. Most of those little chintsy thin aluminum heatsinks with the fins don't really do much in the way of heat dissipation, I have found. If you really want to take away some heat, a huge mass of metal does the best job, in my humble opinion. Chuck > > >---- Original Message ---- >From: [email protected] >To: [email protected] >Subject: Re: [neonixie-l] Nixie Clock Cool Project- a few questions >Date: Wed, 08 Oct 2014 16:46:01 +0200 > >>Hi, >> >>Dman777 wrote: >>> 4) I don't understand why, the heat concentration is in the dead >center of >>> the clock, but the source of what I think is the source of the >heat...the >>> 7805 voltage regulator... is of to the side of the source of the >heat >>> concentration area. >> >>The 7805 only powers the electronics, which I expect draws very >little >>current, so the regulator will remain cool. >> >>I think the heat source might be the MOSFET in the switching power >>supply for the nixie voltage. Unfortunately it's the rather common, >but >>not very good MC34063-based design, you can see the schematic in the >kit >>instructions here: >><http://www.pvelectronics.co.uk/kits/LTC1040/LTC1040_v5.pdf>. They >use >>an IRFD220 MOSFET which has way too high R_DS,on for this >application IMHO. >> >>If you don't want to replace the MOSFET (which wouldn't look too >good as >>I don't think you will find a better replacement with the same >>footprint), having a fan blow air onto it might indeed be a good >idea if >>you can stand the noise. >> >> >>Best Regards, >>Arne >> >>-- >>You received this message because you are subscribed to the Google >Groups "neonixie-l" group. >>To unsubscribe from this group and stop receiving emails from it, >send an email to [email protected]. >>To post to this group, send an email to [email protected]. >>To view this discussion on the web, visit >https://groups.google.com/d/msgid/neonixie-l/54354E29.4030209%40blink >enarea.org. >>For more options, visit https://groups.google.com/d/optout. >> $4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See http://www.All2Easy.net for more details! -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/380-22014103815566516%40all2easy.net. For more options, visit https://groups.google.com/d/optout.
