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circuit help on MC14528B


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XBoy 
Member - Posts: 3
Member spacespace
Joined: January 29, 2004
Location: Canada
Posted: January 30, 2004 at 12:30 PM / IP Logged  
How could I modify the following sequential circuit so that it sequences dependent on a signal wire? (I don't want my brakes to sequence.)  For the signal, I will capture the turn signal activation. 
 
Given that, how could I make this circuit have two behaviors?  sequence delay and no delay?   Do I set the resistances to 0 if I want no delay?
 
 
thanks
 
superchuckles 
Copper - Posts: 89
Copper spacespace
Joined: December 29, 2003
Location: United States
Posted: January 30, 2004 at 9:19 PM / IP Logged  

assuming your circuit relys on the normal signal flasher to turn power off then re-energize it to restart the sequence, you shouldn't need to modify it at all, since when you hit the brakes, the lights will sequence 1 time, then stay lit until you release the brake pedal. 

XBoy 
Member - Posts: 3
Member spacespace
Joined: January 29, 2004
Location: Canada
Posted: January 31, 2004 at 3:34 PM / IP Logged  

I dont want the lights to sequence when I hit the brakes.  I want all the lights to turn on at once when I'm braking.

Looking at the circuit more closely I see if I hook the RESET line to ground, it should bypass the timers, thus making all the lights go on without delay when power is applied.  Is that correct?

MC14528B datasheet

http://rocky.digikey.com/WebLib/On-Semi/Web%20Data/MC14528B-D.pdf

superchuckles 
Copper - Posts: 89
Copper spacespace
Joined: December 29, 2003
Location: United States
Posted: February 01, 2004 at 2:33 AM / IP Logged  
ok, there's a couple of other things you need to think about too, other than the sequencer itself, because, when you hit the brakes, you're still going to want the turn signal (if one is on) to sequence whichever direction you have it set for, while the brake stays steady.  the simplest way to do that, is to seperate the brake and turn signal circuits (since the brake light power runs from the switch at the pedal, up the steering column to the turn signal switch mechanism, i would pull the wire at the pedal switch and run it from there to the back of the vehicle, wherever you're sequencer is).  you see, what you need is, a way for each sequencer to know whether the incoming power is to be sequenced, or to remain steady.  the easiest way to do that (since you may be hitting the brakes and turn signal simultaniously) is having them come in seperately, then building a logic relay block to determine sequencing.  here's where it might be problematic.... the turn signal input is pulsed from the standard turn signal flasher... a solution would be, remove the flasher, and just plug a wire with two spade connectors on it in place of the flasher (now it wont flash, turn signals remain on "steady"), then, put a flasher on each of the output wires coming from the turn signal switch (so the fronts and the dash lights will flash) but - make sure the wires going to the rear are hooked up BEFORE the flashers, so they have power that is on "steady".  now, you put the turn signal power wire feeding a relay on each light, that brakes the circuit for that light that would let power from the brake circuit power them.  now - to make your lights remain on steady for the brakes, just put a diode on each light, which those diodes are fed from the relay i just mentioned, when it's in the "off" state, from the brake light switch.  this way, even if both are on, the turn signal power clicks the relay on, which disconnects that light from the brake light circuit, and powers the sequencer circuit.  once the turn signals are shut off, the relay closes and reconnects the brake light circuit.  it's simpler than it sounds.... if i've got some spare time here in a bit, i'll make a new schematic that will lay it all out for you if that text is too much to follow.
superchuckles 
Copper - Posts: 89
Copper spacespace
Joined: December 29, 2003
Location: United States
Posted: February 01, 2004 at 5:38 AM / IP Logged  

ok, i made a modified circuit diagram for ya if ya need it....but it's too big to post here with the 30k limit, so - if you need it, email me at savage_american@hotmail.com  with the word SEQUENCER in the subject line, and i'll email it back to ya (it's only 215k)

if you don't put the word SEQUENCER in the subject line, your email will be deleted without me ever seeing it, so don't forget that

XBoy 
Member - Posts: 3
Member spacespace
Joined: January 29, 2004
Location: Canada
Posted: February 02, 2004 at 2:51 PM / IP Logged  
Yes, that is right that I want to the turn signal to blinkblink even when I hit the brakes, which I said I will capture the turn signal activation and use that to "switch" the circuit into sequence mode. 
 
However, this brings the following issue, what diodes should I use that are rated for this application?
 
I bought some 6A rectifier diodes and I tested them out with a multimeter and I see a big voltage drop.  I'm not even sure if its wise to run the brakes at sub-12V levels (safety reasons)??  circuit help on MC14528B - Last Post -- posted image. 
 
Initially I was considering using diodes and a relay, like your aforementioned solution (thanks btw!), but I wanted to see if I could simplify things (smaller footprint, fewer parts, etc), which lead me to ask if I could just switch on the RESET line on the MC14528B chip to toggle the activation...
 
 
 
 
 
 

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