I need about 5% duty cycle pulse of about 1 sec time period. A second pulse required should be of same characteristics but delayed by a duration by about the 'on' time of the first pulse. ie I need to delay the pulse. Need a simple solution please.
A simple job for a small micro.
Or three monostables.
-- Bill Sloman, Nijmegen
--
One astable and a single one-shot will do it:
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A one second delay is a bit long for a bipolar 555 - one ot the CMOS variants mgiht be a better choice, or the HEF4047 for those of us who have never soiled our hands with a 555.
-- Bill Sloman, Nijmegen
-- The point wasn\'t that a one second pulse is a bit long for a 555 (which you\'d know it wasn\'t if you ever soiled your hands on a 555) it was that three one-shots aren\'t needed since an astable and a single one shot will do, so your advice was flawed. The HEF4047 is severe overkill from at least two points of view, the first being that two 4047\'s are more expensive than two 555\'s (check Digi-Key) and two 555\'s will fit in the same space as one 4047 (plus two pins). Plus, K.I.S.S. applies.
Who needs a 555 when you've got a PIC.
-- Fuck you, you elitist little cocksucker. Who needs a PIC when you don\'t know the instruction set, you don\'t have an assembler or a compiler or a programmer, and you\'ve got to get something running in an hour or so and you\'ve got a couple of 555\'s and enough different R\'s and C\'s laying around to work out the time constants you need for a one-off? You figure it out, Sherlock. If you can.
The 555 data sheet does claim that the part can take 10M timing resistors - the worst case 0.25uA threshold current is only specified at 25C, but presumably mainly depends on the current gain of the input transistors, which doesn't change all that much with temperature - so 1 sec would be okay. I would know that if I'd siled my hands on a 555 recently - the last time I looked at the despicable part was around
1975 and the general distaste lingers longer than the technical details.It wasn't advice as much as an observation - three monstables would work just as well as an astable and a monostable, and requires marginally less thought.
The 4047 isn't that much more expensive than the 555 Farnell lists a bunch of both parts - the 555 is marginally cheaper - in unit volume
0.51 euro to 0.34, which is scarcely severe. At 500-up and its 0.168 versus 0.153.The smaller size of the 555 reflects the smaller number of options availalbe - no complementary inputs and outputs, for instance, which rather subverts your claim to be keeping it simple with a 555.
-- Bill Sloman, Nijmegen
Now, now, Jim.
But sometimes you feel like a PlIC and sometimes you don't.
Gees, lighten up!
-- Keith
Whoever needs > 25 mA out. Or Vout >5 With no footprint available. Or someone who has 555's on hand and is out of PICs Or someone showing 555's to a newby or to some asshole who thinks PICs are the only answer. Ed
Oh dear, forgot to take your medication again?
-- Typically Slomanesque. You make up your mind and then refuse to budge even when presented with evidence which makes your stand look foolish. What do you still find so objectionable about 555s? Or, for that matter, their CMOS counterparts?
-- Blow me.
-- 50%...
-- John
I never said a PIC was the only solution, there's Atmel, Freescale and a host of others. Getting good results from a 555 for these long times isn't easy or cheap. If you want to see a real asshole adjust your lighting.
Damned if I can remember, and I'm not going to do half a days research to work it out again, despite the charm and courtesy of your invitation.
Absolutely. I've mostly work on high value stuff intended for low volume production - a couple of hundred units a year or less - where the cost of the design work is a substantial fraction of the total production costs over the life-cycle of the unit.
Keeping the design transparent and comprehensible is an important part of keeping the desing costs to a minimum, and minimises questions from final test and the service engineers once the unit is in production.
Applying design rules appropriate to 100,000 unit per year production to the design of one-offs may look professional in Austin Texas, but it looks more like mindless posturing from here.
-- Bill Sloman, Nijmegen
I know you didn't mean that. You couldn't think of anything more intellegent to say I guess.
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