Timing Circuit
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From: Barry Lennox on 30 Jan 2006 14:05 On 29 Jan 2006 07:12:13 -0800, "Jimbo" <James.Wyninegar(a)gmail.com> wrote: >I need to design a circuit that I can tell it to start (digitally), and >then it will tell me when 10 minutes have passed. I just need to be >pointed in the right direction. What's the difference bewteen a >timer/clock/counter. I have a good understanding of circuit theory but >does anyone know of a good IC that can be surface mounted (and is >cheap) that I shoulod use. Any help or tips are greatly appreciated I built quite large numbers of a semi-smart battery charger that used the SMD 4541 timer to generate 14 hours on time. With a decent R and C in the oscillator, the end time never varied by more than +/- 3-4 minutes, or better than 1%. The divider chain lets you select divide by 256,1024,8192 or 65636, and it has a couple of neat control features, dirt cheap too, IIRC, about $1 each. Barry Lennox
From: Jimbo on 30 Jan 2006 14:04 OPPS... OK I think I understand what you saying. By using a Microcontroller there is probably a lot of other logic I can replace as well. I'll have to sleep on that one. Perhaps I'll design the product both ways and then make a comparsion. I don't think I have enough experience at this point to simply make a "judgment call".
From: Rich Grise on 30 Jan 2006 17:44 On Mon, 30 Jan 2006 11:04:47 -0800, Jimbo wrote: > OPPS... OK I think I understand what you saying. By using a > Microcontroller there is probably a lot of other logic I can replace as > well. I'll have to sleep on that one. Perhaps I'll design the product > both ways and then make a comparsion. I don't think I have enough > experience at this point to simply make a "judgment call". Well, you've got a lot of options: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=74 And they show the list prices in their parametic charts, too. Have Fun! Rich
From: Spehro Pefhany on 30 Jan 2006 18:34 On 30 Jan 2006 10:58:04 -0800, the renowned "Jimbo" <James.Wyninegar(a)gmail.com> wrote: >microcontroller? I've programmed them before but I don't know of any >that are as cheap as these other chips. Also, I'm doing this to pay my >way through grad school and I'm working with a very small upstart so >any development boards/software is out of the question becuase of the >price. This is going to be a "large volume"/"low margin" product so >every extra dollar we can squeeze out of the design will have a huge >impact on the bottom line. Are you thinking about something like the >6811 or 6812? There are sub-dollar parts (qty. 100) that can exceed your accuracy spec with no external parts (internal calibrated RC oscillator) and (most important) NO manual trimming or accuracy testing. By using an 8-pin part with an external resonator you could get 0.5% accuracy for about 65 cents (qty. 100)- eg. ATtiny11. You'd have a few I/Os left to play with, can add additional functionality cheaply, and the circuit will become more difficult to copy. Seems like a no-brainer. If the startup will pay you something for the couple of weeks it will take you to figure this stuff out (almost all learning curve), you'll both be ahead. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Peter Bennett on 30 Jan 2006 21:42
On 30 Jan 2006 13:28:08 GMT, "John B" <spamj_baraclough(a)blockerzetnet.co.uk> wrote: >On 30/01/2006 the venerable PN2222A etched in runes: > >> >> "Jimbo" <James.Wyninegar(a)gmail.com> wrote in message >> news:1138570597.321014.296350(a)z14g2000cwz.googlegroups.com... >> > Is there a "system" for the naming of the IC out there? I keep reading >> > things that tend to "hint" that there is a systematic way of naming >> > these things. Isn't the formation usually "LETTERS" + "NUMBER" + >> > "LETTERS". Have any idea as to the method these things are named? >> > >> >> The first 1 or 2 digits is usually the heater voltage. >> >> Regards >> PN2222A > >Actually the first letter is the heater voltage and the next one or two are the construction. For >example ECC83 is a 6.3VAC heater dual triode and ECF86 is 6.3VAC heater triode/pentode. But an ECC 83 is a European 12AX7, which has a centre-tapped 12 volt filament. -- Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca new newsgroup users info : http://vancouver-webpages.com/nnq GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca |