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Noob here wanting some help

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91 XR7

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Tried to get help on another forum but "Automotive modifications" was a no no? even thou i'm technically not modifying a car when i'm building the car from scratch

Basically a Noob here, but have a basic understanding and just need help on how to implement a secondary delay on a delayed off circuit.

I wanted to try and build the Circuit on Bowdens Website but the boss wanted something more prebuilt so we ended up with a CanaKit UK197. But the problem i found is the quick off then back on that it does as you ground the trigger during the delay (Resetting of the timer). So i like to fix this issue so it doesn't do that. And i was thinking of implementing the circuit on Bowden's site on the output side before it goes to the transistor.

I truly hope this makes sense to people

**broken link removed**

Q1 = 2N4123
C6 = 100uF
R5 = 1000 ohms? (Brown, black, red, gold Stripes)
Relay = 200 ohms? (PN :HJR-3FF-S-Z by Tianbo)

This circuit is going to be used the run a secondary electric water pump in a car that's a rear engine from Radiator setup that's only needed mostly at idle. Just didn't want to have the water pump turning off and on in traffic like situations so wanted a delay of like 20-30 seconds before the pump shuts off and is reset when the car came back to idle.


Thank you
 

jpanhalt

Well-Known Member
Most Helpful Member
Welcome to ETO.

If I understand your question, you want to prolong the pulse of the 555 by retriggering it, but when you do that with the UK197 circuit, you get a short glitch. If that is the case, search for "retriggerable 555," and you will find a lot of hits, including the circuit of the UK197. Here is just one: **broken link removed** Scan down to schematic #9. Note that it discharges the timing capacitor without resetting the device. Here's another approach with fewer components: http://en.f-alpha.net/electronics/i...-on/experiment-13-retriggerable-monoflop.html In the UK197, the reset pin (#4) is tied to the trigger, thus on retriggering the UK197, the whole device is reset, which probably accounts for the glitch you see. I have not tested any of the retriggerable circuits presented above.

Since the "boss" wants an off the shelf answer, you may have to find another monostable controller (i.e., a retriggerable one) or do a little re-wiring of the UK197.

Have I understood your question correctly, and is the momentary glitch really a problem?

John

Edit: And here's another from Bill Marsden: http://forum.allaboutcircuits.com/c...ent.php?attachmentid=15852&stc=1&d=1265055550
 
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91 XR7

Member
In the UK197, the reset pin (#4) is tied to the trigger, thus on retriggering the UK197, the whole device is reset, which probably accounts for the glitch you see. I have not tested any of the retriggerable circuits presented above.
Since the "boss" wants an off the shelf answer, you may have to find another monostable controller (i.e., a retriggerable one) or do a little re-wiring of the UK197.
Have I understood your question correctly, and is the momentary glitch really a problem?

Thank you for the reply

Yes i do believe you understood my question/concern? it is just, least at this time, the momentary glitch where the Circuit is completely reset that's the problem.

Well at this time i'll have to try and rewire the UK197 to make it work, Since it's already been modified anyways (the Power In jack , the Switch and Diode Bridge have been removed, along with a 7809 installed to keep the voltage in range (9-12 volts) Now Have to see what it'll take to modify the circuit already there to work, I'm almost thinking the one on the f-alpha.net site you link too may be the easiest?

Thank you again
 

jpanhalt

Well-Known Member
Most Helpful Member
The circuit you mention has a low parts count. Marsden's circuit is quite similar and uses a transistor to create the negative pulse from a positive pulse. Try the simple one you mention and see if the glitch is gone. Then, if you need to run it with a positive pulse, you can switch to Marsden's circuit.

John
 

91 XR7

Member
Wondering in the Uk197 circuit it has a capacitor C2 on the trigger circuit, and the other circuits posted don't seem to have them, should remove it or just keep it?

Thank you again for the help
 

jpanhalt

Well-Known Member
Most Helpful Member
The purpose of that capacitor is to get a short negative blip. Bill Marsden's has it.

As I said, I have not tried any of those circuits . The goal in each circuit is to discharge the 555 timing capacitor, not reset the whole chip as in the circuit you bought. I don't know where you are suggesting to add the capacitor to the second circuit. If it is in the wrong place, it will block discharge of the timing capacitor and probably not work.

If you go with any of the circuits, I would suggest building it as shown. Then, if it works, you can consider modifications. How long will your input pulse be compared to the shortest output pulse?

John
 

91 XR7

Member
The purpose of that capacitor is to get a short negative blip. Bill Marsden's has it.
If you go with any of the circuits, I would suggest building it as shown. Then, if it works, you can consider modifications. How long will your input pulse be compared to the shortest output pulse?

Well i have rebuilt the UK197 circuit to be like the one on the f-alpha.net and it now doesn't reset the whole circuit which is nice, but it has brought up another concern (go figure)

this is how i'm planing on hooking it up into the car.

Positive: From the Ignition switch "run" position
Ground: Will be from a thermo switch that's self grounded at about 190 degrees F
Trigger: From a idle position switch on the throttle body (grounded)
Trigger 2: High speed / second cooling fan command from ECU (Ground trigger)
Output: Will be using the UK197 setup with the Relay to send a Ground signal to another relay in the front of the car

The issue at this time is that if i simulate it being hooked up (via a car battery) if i have the Power hooked up and i Ground the trigger wire the circuit turns on with out the ground being attached.

I may hunt down a 2 Pin coolant switch that i can run ignition into one pin, and the other pin to the Positive of the circuit. but most are shelf grounding single pin switches so it'll be a royal PITA so if i can fix the circuit i'll be happy

Thanks to you i'm 95% there now, and i greatly appreciate it.

thank you again
Kevin
 
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91 XR7

Member
I think i may just add an relay to turn on the positive side once the coolant temp comes up to a set point (190ish) and have the ground grounded constantly.

Just seems to be easiest at this time and moment. But if it can be done with out that be nice to know for version 2.0 of the Booster pump control :)
 

91 XR7

Member
Before the final install wondering if anyone has a brighter idea then my idea when it comes down to fixing the "trigger" turning on the circuit even when the unit isn't grounded?

As of right now this the thought

Minor change;

Ignition to 3 amp fuse, then to timer positive input and to a relay "86" terminal.
Ground to timer circuit, thermo switch and timers on board relay
Thermo switch to relay "85" terminal
Idle switch to relay "30" terminal
Relay "87" terminal to timers trigger



Thank you,
Kevin
 
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