Post by thread:[OT]:power supply suggestions

I could do with some help here.. I am driving a small thermal printer with cutter and need a 7.7v @5A for 3mS. I thought I might use an LM338 voltage reg stright out of the ST-Thomson book. But I'm not happy with that route. Any suggestion where there is a better approach? -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

On Thu, Jan 31, 2002 at 04:34:20PM -0000, zantos wrote: > I could do with some help here.. > I am driving a small thermal printer with cutter and need a 7.7v @5A for > 3mS. I thought I might use an LM338 voltage reg stright out of the > ST-Thomson book. But I'm not happy with that route. > Any suggestion where there is a better approach? Why don't you like that approach? It's the least complicated. The second least complicated is using an LM317 along with a PNP pass transistor. The benefit will be that you can use a beefier transistor that can pass more than 5A, and that the LM317 can share an amp and change of the load. Check out the section labeled "LM317T Voltage Regulator with Pass Transistor" here: http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm Other ideas include building a simple switcher (LM2574) driving a external pass transistor (probably a low Rds(on) p-channel MOSFET). It will eliminate the heat dissapation issue due to being a switching regulator. Be careful about output capacitors or you'll get a great oscillator. Check the ESR required. But unless you have a really good reason, the simplest solution probably is the best. BAJ -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

> Why don't you like that approach? It's the least complicated. Well I can't ague with that point. I just thought it was too simple to be effective. I'll stick with that approach. I like the LM317 also. Thank for replying z -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

On Thu, Jan 31, 2002 at 07:09:21PM -0000, zantos wrote: > > Why don't you like that approach? It's the least complicated. > > Well I can't ague with that point. I just thought it was too simple to be > effective. Just make sure you have sufficient input volts/amps, capacitance and heatsinking. 3mS isn't a long time for heavy current draw so the part shouldn't heat too much. > > I'll stick with that approach. I like the LM317 also. Well I've always treated the LM338 like an LM317K. BAJ -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Use a large capacitor charged through a R from your normal supply. You can probably exceed the voltage if the time is shorter, since it's a coil (no?). Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Something to try. Thank for the reply. z ----- Original Message ----- From: "Peter L. Peres" <EraseMEplpspam_OUTTakeThisOuTACTCOM.CO.IL> To: <PICLISTspam_OUTMITVMA.MIT.EDU> Sent: 01 February 2002 13:42 Subject: [OT]:power supply suggestions {Quote hidden}> Use a large capacitor charged through a R from your normal supply. You can > probably exceed the voltage if the time is shorter, since it's a > coil (no?). > > Peter > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads