As I remember, they were really fussy about the lube used on the wires. The best luck I had was a bottle of sperm whale oil from the old diablo hyper typer days. -----Original Message----- >From: Spehro Pefhany >Sent: Aug 25, 2008 4:57 PM >To: piclist@mit.edu >Subject: Re: [EE]: Back-EMF catch diodes slowing solenoid response > >Quoting Philip Pemberton : > >> Hi, >> Well, I'm two days into my summer holiday, and I've already run out of things >> to do on my current projects. So I figured I'd resurrect an earlier project >> that I put on the backburner ages ago. >> >> A good few years ago, I bought a pair of Epson M-180 series impact printer >> mechanisms. These are basically 24-character dot-matrix printers which use >> five horizontal solenoids instead of the more typical single 9-pin vertical >> head. The idea being that it speeds up printing, and allows graphics printing >> where necessary. It's actually pretty speedy... for a 1980s vintage piece of >> kit. A lot more power hungry than my Seiko MTP-series thermal mechs, >> and a bit >> of a pig to design hardware around. Typical Epson kit really, fussy >> and finicky :) >> >> From my project notebook, I was having issues with the print head solenoids >> holding down for too long: >> >> > Print quality still terrible. P/Head solenoids seem to be holding >> too long, >> > 1N4001 diode snubber slowing decay. Removed diode - some improvement, but >> > ULN2003 driver failed in short order, probably due to back-emf. Needs >> > further work. >> >> I've been digging through Horowitz & Hill, and scanning Google for about 40 >> minutes now, and haven't found any decent material on back-EMF >> suppression for >> transistors used for driving inductive components. I've found tons of >> references that boil down to "just use a 1N4001", a few that actually admit >> that a '4001 will slow a relay's switch-off response "significantly", but >> nothing on what to do to speed things up. > >...snippage.. >> >> Thanks, > > >Lose the diodes. Connect a 47V zener between COM on the ULN2003A's and ground. > > >Best regards, >Spehro Pefhany >-- >"it's the network..." "The Journey is the reward" >s...@interlog.com Info for manufacturers: http://www.trexon.com >Embedded software/hardware/analog Info for designers: http://www.speff.com > > >-- >http://www.piclist.com PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist