[neonixie-l] Re: Dummy load
For instance... On Semi FDD3N40 or FDU3N40... 400V / 2 A / 30W in DPAK or TO-251... I usually have a few FDD3N40 on hand and have used them in multiple designs. There are of course many good alternatives! -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/439d83d5-b4a0-46d9-b111-d8fa2626f686%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: Dummy load
Hi Paul, I also like the "simple" current sink circuit approach, but it usually takes a few more parts to get a stable circuit... the most basic design with just a resistor, transistor and op amp tends to "sing"! And there's also some parts selection to be done. See Linear Tech Application Note 105, figure 200 on page 108: https://www.analog.com/media/en/technical-documentation/application-notes/an105fa.pdf Here's where I might start on adapting the Linear Tech design... Change the 1 Ohm resistor to 10 Ohm for a 1 V / 100 mA control voltage. Will need a suitable MOSFET for the application… I filtered N-Channel MOSFET on DigiKey looking for the following: Vdss between 250 and 400 VDC... I regularly use supplies at 180V and occasionally push 300V. Make sure you have some margin. Power Dissipation between 25 and 40 W… I assume at least 100 mA at 200 V for the load… plus margin… plus a suitable heat sink! Continuous current between 1.7A (lowest available value by the time the previous filters were in place) and 3A (provides a few more alternatives!) I also suggest a 10V to 12V supply for the op amp to assure ample gate drive voltage. Some of these MOSFET need a bit of drive to get to higher currents… 5V might well be sufficient, but need to check the MOSFET data sheet. Select an op amp for operation to the negative rail for low current settings and a suitable V+ supply range. Anyway, that's a start! Enjoy Bob -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/8205e377-2d26-44e2-ac8f-3d04e8797564%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: Dummy load
I also like the simple current sink circuit approach, but it usually takes just a few more parts to get a stable circuit... the most basic design with just a resistor, transistor and op amp tends to "sing"! See Linear Tech Application Note 105, figure 200 on page 108: https://www.analog.com/media/en/technical-documentation/application-notes/an105fa.pdf You might change the 1 Ohm resistor to 10 Ohm for a 1 V / 100 mA control voltage. -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/cb6ae59b-7044-4b45-9f25-9f0054209578%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: Dummy load
I think that, as David says, an OTA is the ideal solution for you... a small opamp, plus a MOSFET or a bipolar transistor, with a reasonable heatsink will do fine. On Thursday, November 22, 2018 at 2:44:01 PM UTC-3, Paul Andrews wrote: > > Hi > > I’ve been looking for an electronic dummy load for a while, but I can’t > justify spending money on a piece of lab equipment. There are several cheap > dummy loads around, but most of them can’t tolerate the sorts of voltages > that a nixie power supply needs to produce. > > A few days ago I came across this one: > http://www.voltlog.com/voltlog-119-new-150w-dummy-load-review/ which > looked perfect, until I read the granularity of the current settings - way > too coarse. So I was wondering if it might be possible to take one of these > and modify it to provide loads more in the range of those needed to test > nixie power supplies - e.g. a few mA to a few hundred mA in 1mA increments. > > If it’s a possibility, I might just get one and then start trying to > figure it out. -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/cbfc8d5a-cbf9-4336-926f-988649e8a98f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
