design help

jamesgangnc · 2009-02-24T13:17:20+00:00

I'm ok with fixing and adapting circuits but not so good with design. I've come up with an electronic switch circuit but I think it could use improvement. The goal is to turn on a 12v relay with a switch that is closed when off and open when on. The switch also has to have one leg grounded. It's a pressure switch with a single terminal. I also want the relay to stay closed (on) for a couple minutes when the switch goes from on (open) to off (closed). Here's what I've got now and it does work. But I had to use a pretty big capacitor and I'm still only getting about a minute of delay when going to the off state. Because I can't make the 10k resistor any bigger. I'm thinking that it is likely possible to get a longer delay and do it with a smaller capacitor if I was better at designing this. The other flaw is that this slowly lowers the voltage to the relay until it drops. The relay stays pulled to about 3 to 4 volts. I also suspect there is a better way to keep it fully on until the rc timer expires. Thanks in advance for any suggestions :-)

J

John Larkin 17 years ago

delay so

Batch files and README type stuff, and anything unique to the project, yes. The assembler and text editor and builder utilities are archived in our TOOLS folder on one of our servers, backed up to DVDs weekly. Any versions get a separate folder, so we always have the old ones. We must have hundreds of backups scattered all over the state by now.

There's no problem figuring out which tools are needed to rebuild a thing. The FPGAs are a bigger problem... we have some Actel designs that used Win3 Orcad under DOS with dongles, and *nobody* can rebuild them.

The advantage of simple tools is that they are easy to archive and revive. DOS boxes will live forever.

And engineering isn't allowed to build production units. Firmware gets to manufacturing as a formal document release on a CD; our librarian documents the release and puts the files on the library server.

Useless to me, except that the buggy results can be annoying.

We are living in the Dark Ages of computing.

John

Vote

J

James Arthur 17 years ago

Nice idea. My version had a common emitter driver, adding that and a base resistor to the parts count.

That set it behind in the parts-count derby, so I dumped it. Yours is better.

Cheers, James Arthur

Vote

J

JosephKK 17 years ago

John and John, instead of spouting you could just test it.

Vote

J

James Arthur 17 years ago

Good point.

Cheers, James Arthur

Vote

J

JosephKK 17 years ago

That's why so many use AACricuit for the task.

Vote

N

Nobody 17 years ago

That only works if it's feasible to comprehend the design in its entirety. For a few KiB of uc code, that's realistic. For large scale desktop or server packages, it isn't.

For complex software, if you can't function without detailed knowledge of the entire system, then you simply can't function. Even if it was feasible to comprehend the entire system, it might take months or even years to do so, and changes will happen faster than you can absorb them.

You could have to re-write whole swathes from scratch to port the software to a different architecture, or even to a different version of the OS.

In a complex software package, you could have more code than that for a single dialog box. You could realistically have more than that just in the installer.

Lumping the design of microcontroller firmware and the design of application software together as "software" is like lumping the design of a microwave transceiver together with the design of a PC motherboard as "electronics".

Vote

J

JosephKK 17 years ago

Naw. Dis-parity. It is for bragging rights only.

Vote

K

krw 17 years ago

Well, there's the BAV170.

formatting link

Vote

J

JosephKK 17 years ago

Sure was, and the machine had cores that i could thread 4 wires through even today. (full 3-D core memory)

Vote

J

James Arthur 17 years ago

Vote

J

JosephKK 17 years ago

Yes, Escheresque terrain and buildings ("Ascending and Descending") were quite common back then.

Vote

J

James Arthur 17 years ago

Yep. Handy.

Vcc -+- | .---------------------o \\ | |_ o o .-. )| | | R1 )| | | _)| '-' | | ||-' | D1 |||---o-----o---||-+ | | | | \\ o | .-. R2 | \\ C1 --- | | === \\. --- | | GND o | '-' | | | === === === GND GND GND (created by AACircuit v1.28.4 beta 13/12/04

formatting link

)

Vote

J

James Arthur 17 years ago

Vote

J

John Larkin 17 years ago

I might this weekend. I just shipped a new gadget today that I've been at all week, and I'm whupped at the moment.

John

Vote

J

James Arthur 17 years ago

Nearly choked me on me sourdough crêpe, 'at one did.

Cheers, James Arthur

Vote

J

John Larkin 17 years ago

This is sci.electronics.design. Most of the stuff we do meets that description. Why abstract setting a bit in a register (which I've seen people do) when you can set the bit in the register?

OS? What OS? And it's unlikely that we would port a working product to a new CPU just for fun.

Well, as I've said, I elect to not do stuff like that. And given that decision, I don't need an RTOS and C++ to set and clear bits.

This is sci.electronics.design.

John

Vote