design help

John L, Methinks you need to revisit the original SOW, before throwing stones...

"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 :-)"

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Probably good enough for lots of apps. Turnoff is slow enough that it doesn't need a flyback diode.

It can be flipped into a follower, too...

in which case the relay dropout voltage contributes to the time delay.

John

I'm sure you and Rich will post some great circuits and show us how wrong we are.

John

You threw stones at John F, then posted a very soft transition solution... did you not?

Did you bang your head badly during that skiing spill ?:-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
With all this hope and change, all you need is a dab of mayonaisse
and you\'ll have a tasty lunch on which you will choke to death.

I prefer the version with hysteresis for being easier on the output transistor, but I screwed up--the output's inverted, I used 'R3' twice, and I left out the diode across R2.

I'll try to redeem myself.

+12v -+- | .-------------------+----------+ | | | [R1] [R3] | | | |

--
Onward through the fog. Seems a couple of us got it, you not included,
first time out.

[snip]

Bwahahahahaha! Damn! Almost snorted wine up my nose :-(

Bwahahahahahaha!

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

If we knew what we were doing, it wouldn\'t be called research...
                    -- Albert Einstein

Now now boys, we've got better things to jaw about. Check out the Newshour on PBS re: the budget. Stunning.

The Nightly Business Report too. Yikes.

Cheers, James Arthur

I don't want to watch something like that... it would upset me so much I couldn't enjoy the nice (French-style) pot roast about to be served.

And I'm sipping a nice Coppola Diamond Collection 2006 Black Label Claret ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
With all this hope and change, all you need is a dab of mayonaisse
and you\'ll have a tasty lunch on which you will choke to death.

Enjoy!

James Arthur

I make mistakes all the time, some here. And I freely admit the ones that are obvious. We just sometimes disagree on what's actually a mistake.

Get a life. You're turning into an old hen, strutting and clucking.

If I misunderstood the OP's polarities, so what?

Get a life.

John

TWO old hens.

John

I called him an old hen, which is pretty accurate. What's wrong with soft turnoff of a relay? The armature stays seated until it doesn't.

Nope, skiers and motorcyclists don't often land on their heads. That's for snowboarders and horse riders.

Hey, post a relay delay circuit of your own and quit clucking. You're turning into the village gossip.

John

Poor baby ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

If we knew what we were doing, it wouldn\'t be called research...
                    -- Albert Einstein

It can be done though, I know. I don't crash often, but coming off the side of a slope into rough snow at very high speed once, I jumped off a little mound and landed on another mound almost 10 metres away... except it was a minimal bit of snow covering a bush, into which my skis vanished and stopped. I flew forward out of my bindings and did a head-plant deep into the soft wet snow a further 8 metres away, and distinctly recall my neck being in a strange and unusual position as my whole body flipped violently over the top, wondering if this was going to be my last thought. Landed flat on my back and got up just dazed and with a stiff neck, and had to climb back up to get all my stuff.

Tell that to Sonny Bono. Oh... that's right... you can't.

Tell that to Gary Busey. Oh... That's right, he ALSO hit his head from a bike spill.

No, they may not 'land' on their heads, but they sure do have a high instance of head trauma involvement in such circumstances. So at some point while they are wiping out, head impact occurs.

He skied into a tree. By the time he landed, it was pretty much over.

It can be done, especially if you ride without a helmet like GB. But most ski and motorcycle dumps are pretty much horizontal. If you are going really fast, you can tumble and then it can get nasty.

Sure. But falling off a horse is a lot more dangerous... good chance of vertical impact. And snowboarders, going fast downhill across the slope, can catch an edge and get flung down a slope head-first.

This time on the mountains, I saw a LOT of people, especially snowboarders, wearing helmets.

John

KXP1624, 24 pin, 14" fanfold. Works great. I go through a box of paper and a ribbon per project, roughly.

We also have an HP 14" fanfold inkjet, but I like the Panasonic better. I've heard that there are serious 14" fanfold laser printers, for serious money. Maybe if I get rich some day...

John

Sorry, they violate the 6-character symbol limit.

John