Thanks Nick, I'll try that. Back in my day I mostly used 4000 CMOS, I didn't do much with TTL.
On Wednesday, 27 September 2023 at 11:23:17 UTC+1 Nick Sargeant wrote: > I'd agree with the above. To make sure you are avoiding any indeterminate > states, pull all of the inputs up to +5v with a resistor of about 2k2 to > 4k7. Then, for the inputs you want low, jumper those inputs to ground. The > pull-up resistors will mean you get a good solid '1' without the jumper, > and a good '0' with a jumper to ground. > > When designing with TTL,back in the day, we tended to work with negative > logic as a preference, because of the nature of the inputs being connected > to the emitters of bipolar transistors. > > > > On Wednesday, 27 September 2023 at 10:14:46 UTC+1 Craig Garnett wrote: > >> I tried those suggestions and nothing changed, there's around 4ma total >> through the LEDs now so it shouldn't be in meltdown mode. >> >> On Tuesday, 26 September 2023 at 17:45:06 UTC+1 Craig Garnett wrote: >> >>> Thanks, >>> I'll give those suggestions a go. >>> >>> On Tuesday, 26 September 2023 at 16:05:17 UTC+1 gregebert wrote: >>> >>>> 74xx TTL devices have a rather high input-low current, on the order of >>>> 1mA, so you should use a much smaller pulldown resistor, say 100 ohms, or >>>> perhaps none at all. Logically, it should not be possible for more than 1 >>>> output to get driven low on the 7441, but that only applies if all >>>> parameters in the datasheet are met. I suspect that the 100K pulldown >>>> isn't >>>> really pulling-down to a logic-zero, and the IC has gone to some >>>> intermediate logic state which is non-deterministic. >>>> >>>> For the LEDs, I would recommend having a 2K series resistor and driving >>>> from +12 VDC. That works out to around 5mA of current which is enough to >>>> make many LEDs visibly glow and well-below the 7mA max current rating of >>>> the 7441. >>>> >>>> On Tuesday, September 26, 2023 at 6:30:15 AM UTC-7 Craig Garnett wrote: >>>> >>>>> I bought a 74141 on Ebay and I had a bit of trouble with the delivery >>>>> but it arrived eventually so I'm trying to test it on the breadboard. >>>>> >>>>> I've hooked up LEDs from +ve to all the outputs and pulled the 4 >>>>> address lines down to ground with 100k >>>>> >>>>> When I power it up 6 of the LEDS are on and raising any of the address >>>>> lines does nothing. >>>>> >>>>> It doesn't look good does it? >>>>> >>>>> Craig >>>>> >>>> -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/0d97761b-9806-425d-8f2c-a3a6da5d4eeen%40googlegroups.com.
