Rube Goldberge convluted relaus

Status
Not open for further replies.

MrDEB

Well-Known Member
Needed a delay ON circuit that turns on a 60W transformer BUT I have a 12v DPDT relay and a 5V SPST relay.
Idea is the SW1 is depressed thus activating 5V relay (the relay stays ON for 8-10 seconds)that turns on the transformer
Transformer ON turns on the power for the PIC via the 7805
The PIC enables the 2n3904 to keep the power to the 7805/PIC
When the PIC output turns OFF the entire circuit turns off including the transformer.
This is a temp controlled soldering iron w/ auto shut off after non usage of 10 minutes.
Yes I know I could have used a SSR but then HEAT rears its head.
In theory this circuit should? work but there should be an easier way?
 

Attachments

  • rube goldberg.png
    153.5 KB · Views: 147
Why not just have the 12 V relay, and have the pushbutton in parallel with the contacts? You won't need more than 50 ms or so for the circuit to power up, the PIC to start working and to power the relay. The capacitor delay looks like it is a delay off, not a delay on, and I can't see the need for it at all.
 
Reason for 5v relay is I want to control the 12V relay w/ a battery pak (3-AAA batteries)
The delay circuit works as is. Press the button and relay is ON for aprox 8 seconds.
I want to be able to turn OFF the transformer completely. To turn soldering iron ON you press the button which turns on the 5v relay > turns ON the transformer > applies power to the PIC > keeps the transformer ON.
I am looking at using just the 5v relay but don't want to burn up the contacts. Another reason for the heavy duty 12v relay
the 5v relay = 1A 120v 12v = 3A 277v
need to check current draw of transformer. It says 60Watts but want to be sure. If I calculated right it should be just under 2A?
 
Dang it!! the 5v relays are only rated 1a at 120v. I need 2A.
12V battery anyone?? Then I could maybe go w/ one 12v relay?
 
Reason for 5v relay is I want to control the 12V relay w/ a battery pak (3-AAA batteries)
Click to expand...
But why would you want to???

Your supply circuit is a bit iffy!
Why are you using a 24v transformer for a 12v supply?
Why are you using that curious arrangement of diodes to half wave rectify the 24v?
Why is there no smoothing capacitor on the supply? The relay will hum quite loudly at a quick guess.

JimB
 
The 24v ac supplies the heating element in the soldering iron. I need 12v for the relay coil unless I can locate a 12v wall wart then turn it off/on using the 5v relay.
The caps for filtering are added AFTER I get the basic circuit working. The PIC control board has filter caps as well as a 7805 on board already. Need 7.5VDC or more for the 7805.
Reason for a battery is the ability to turn off the entire circuit including the 24v transformer. THINK ENERGY SAVING. Why have the transformer running 24/7
Going to second hand store (Radio Shack dosn't have 5v relays) to locate a 12vdc wall wart hopefully.
 
Your 12V relay is being hit by about 33V peak from the transformer. It might not like that!
I agree with Diver300 in post #2. Simply use a mains-rated pushbutton instead of the 5V relay to turn on the transformer initially and let the PIC turn it off. Only one relay; no battery. So no battery to charge/replace, so even more ENERGY SAVING.
 
Will contemplate but didn't want 110v in my control box.
The transformer/110 are in a separate enclosure on the floor to clear bench space.
The control panel (PIC/LCD ) hanging from shelf. A micro switch detects iron usage. If not used in ten minutes the entire unit (transformer, relays etc) shut off.
POWER CTR ENCLOSURE------6ft------------PIC, LCD ENCLOSURE--18"--iron
If I have 110V in my CTR panel I then have to run another wire, no big deal but didn't want 110v in CRT PANEL (PIC, LCD)
I found a 12v wal wart 500ma.
My revised idea. May not be the best but troling for suggestions.
NOTE I don't want 110 in my control panel. Thats why I thought about batteries. The batteries in the power enclosure. Only four wires from CTR panel to Power enclosure
(2 = 24vac, 2=connected to push button(5v & GRD)
 

Attachments

  • rube goldberg-1.png
    42.6 KB · Views: 122
Should have included a layout

here is my planned layout.
The CTR panel mounted above bench while the transformer etc on floor
This layout may describe why I want a battery pack. The batteries are only used to power up the unit (8 seconds)
 

Attachments

  • layout.png
    149.5 KB · Views: 137
The 12V output is AC and needs to be rectified.
The 12V relay will connect the 24V output to the 12V output. Bang!
 
12vac? its rectified? lost?

maybe mis communication or ?
"The 12V output is AC and needs to be rectified." I think the diodes rectify it?


"The 12V relay will connect the 24V output to the 12V output. Bang!"
Not sure what your refering to. Could ba a bad drawing on my part?
 

Attachments

  • rube goldberg-2.png
    37.3 KB · Views: 125
I think the diodes rectify it?
Click to expand...
No. They rectify the 24VAC. Your 12V wall-wart is (as shown) putting out AC so would need a diode (preferably a diode bridge) to rectify that and prevent the rectified 24V supply (right-hand transformer) from driving current through the wall-wart.

Why not dispense with the 5V relay and the wall-wart and just use a 9V battery and the switch to supply 9V temporarily (a fraction of a second) via a diode to the input of the 7805, so that the micro can power up and energise the 12V relay to switch on the 24V supply?
 
Now that's an idea
Why just a fraction of a second? Why not say 8 seconds. Time for everything to settle down?
Will ponder this idea.
THANKS
 
Why just a fraction of a second? Why not say 8 seconds. Time for everything to settle down?
Click to expand...
Unless you're using umpteen Farads as a smoothing capacitor your 24V power supply will settle down in milliseconds. Consider a transformer winding resistance of 20 Ohm (that's erring on the generous side) and a smoothing capacitor of 1000uF the time constant is 20mS. Add on, say, 50mS for the micro to initialise. So 100mS tops should be enough. 8 secs is way too much. You could add an LED to indicate when the micro has switched on the relay; then just press the button and wait for the LED to light (almost instantaneously).
I have just realised that 9V would probably not be enough to pull in the 12V relay. It would be more reliable to use a 12V battery instead of 9V.
 
MrDEB said:
THINK ENERGY SAVING. Why have the transformer running 24/7
Click to expand...

"Vampire power" is grossly overrated. If you are serious about energy saving, buy a $20 Kill-A-Watt P4400 wattmeter. Now see if you can get that 12V, 500 ma wall-wart to even read ONE watt with an unloaded secondary. It probably won't - this idea that they are all burning off hundreds of watts on standby is a load of BS.

Now consider the amount of energy it takes to make a set of batteries, ship them around the country, deal with them in the waste stream...
 
You seem pretty passionate about this. Care to explane? I think in the end it all adds up and we can help by shuting off what we can. Andy
 
starting with a clean sheet

Found a 9v relay which makes life easier. Contacts rated at 10A or so the data sheet says.
Vampire power is really an iffy source of power IMO
 

Attachments

  • auto shutoff.png
    33.3 KB · Views: 121
That's more like it. I think you could simplify it further, as per the attached.
 

Attachments

  • PowerSaver.gif
    14 KB · Views: 123
WHAT no OFF delay so the PIC has time to take control of circuit?
nice drawing
thanks
 
WHAT no OFF delay so the PIC has time to take control of circuit?
Click to expand...
No appreciable delay needed. Once powered up (<100mS) the PIC should take only a few mS at most to initialise. Its first task then should be to switch on the relay. So from pressing the button to the relay pulling in is just the blink of an eye.
 
Status
Not open for further replies.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…