1. Home
  2. Electronics Design
  3. 555 relay current reducer
  4. Page 2

555 relay current reducer

I said, literally "It will guarantee that most relays hold closed", which is certainly true.

No, it's not. I guarantee that most (ie, >50%) of relays will stay closed at 50% of rated coil current. Which means that, for a given relay, this circuit will very likely work.

I said "most" relays, not "all."

You're nitpicking to be a PITA. Any competant engineer will check the specs for the relay at hand and make sure this circuit will work. Most of the time, it will.

The catch diode forward drop must be considered, of course. And the actual duty cycle of the oscillator, which won't be exactly 50%.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin
Loading thread data ...

That snort is getting worse and worse. Have you seen a doctor yet?

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

I see a salesman on the rise! jamie

Reply to
M Philbrook

Or you can use feedback to guarantee pick/hold.

Reply to
krw

And then you have this!

formatting link

Reply to
M Philbrook

Yep. That's the way to do it. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

formatting link
| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Reply to
Jim Thompson

1995! Was that before digital logic was discovered? 
--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

Yes, needs a diode in series with it, oops

--


----Android NewsGroup Reader---- 
http://usenet.sinaapp.com/
Reply to
bitrex

Diode in reverse-series or whatever, rather

--


----Android NewsGroup Reader---- 
http://usenet.sinaapp.com/
Reply to
bitrex

I think long hair was just starting to be phased out!

Jamie

Reply to
M Philbrook

But it uses a 4:1 current ratio. John's being criticized for 2:1. (IRL, i(drop-out) is closer to i(pull-in)/10.)

Cheers, James Arthur

Reply to
dagmargoodboat

Yes. I almost had it with a 74HC74 one-shot + osc??, but have other things pressing.

Osc. duty sets the PWM. One-shot sets the pull-in interval...

.--------+----. | | | .------. .--o---. [R2] [C2] | PR | | PR | | | Vdd >--|D Q|-- --|D Q|----' === | | | | >--------|> | ---|> | | Q*|----. | Q*|----. | CLR | | | CLR | | '--o---' [R1] '--o---' [R3] | | | | '--------+ '--------+ | | [C1] [C3] | | === === Needs some gluing.

4:1 power is a darn good start, but 3-4:1 current is even better, 'natch.

They should build that into car relays. In normal running my car's got a bunch of coils cooking. Think of the carbon...

Cheers, James Arthur

Reply to
dagmargoodboat

Don't suppose anybody's considered a latching relay? Hold current approaches zero.

Reply to
mike 

--
Indeed, and what's going to happen next is that - even though he 
hoisted himself on his own pitard - Larkin will fight tooth and nail 
to try to change the subject, make it seem like you're the one at 
fault for mentioning his gaffe, an on and on and on.  

Larkin is a very dedicated, practicing narcissist, you see, and will 
go to extraordinary lengths to keep from having to admit to error. 

John Fields
Reply to
John Fields

o

et

l

it was easy enough to understand

NT

Reply to
tabbypurr

Data suggests that relays are typically between 3:1 and 5:1. I'm sure that fuel injectors are heavily characterized. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Gaffe? What I said was literally true.

But if you want to misinterpret it:

Find a DC electromagnetic relay that has specified pickup/dropout voltages, and has dropout voltage above half of rated voltage.

Post a link to the data sheet.

Post that link for us.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

AC-coil relays are preferred in tough industrial apps, like shipboard, because they automagically reduce their own coil current when the armature seats. So they are more reliable than DC relays.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

and it dumps a lot of the energy in the Zener

modern direct injection injector drivers use a more elaborate design not only uses a boosted voltage for the opening but also switch between slow decay for the hold period and fast decay for the turn off

-Lasse

Reply to
Lasse Langwadt Christensen 

--
Wow!... That's a blast from the past in that Larkin's unwavering 
opinion is that latching relays have infinite gain. 

John Fields
Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.