could this be changed?

[Jbroadway]

hi ive found a circuit that i want to ask some advice on its an automatic curtain closer, it says it has automatic mode but i have noticed that it has a 555 timer. i was under the impression that a 555 timer could only do a few minutes at max.

heres the link

1. my question is it possible to change the 555 to make it a 12 hour timer?

2. could i adapt the circuit to 6v input with a small 6v solar panel to recharge the battery?

 

[alec_t]

i was under the impression that a 555 timer could only do a few minutes at max.

That's generally true. In the circuit shown the 555 generates a pulse which is only a fraction of a second.
1) With an extremely expensive low-leakage capacitor (or bank of capacitors), theoretically it's possible; but in practice you would use the 555 to clock a divide-by-n counter IC, perhaps at ~ 1Hz.
2) I don't see why not. Depending on motor type and how often the motor is energised you may find you need quite a large solar panel.

 

[Jbroadway]

it will be a 6v 5rpm motor and id find out what it draws from the battery and usage time to see how much id need to recharge the battery before i make it.

and the bit you said at first totally lost me. is this complex for the simple thing im trying to do?

instead of this design could i use a pic (e.g 18m2) and its internal timer to do the same thing with less components im thinking with the pic all i would need is a motor 2 relays a capacitor and i blocking diode? (is this correct)

 

[alec_t]

and the bit you said at first totally lost me. is this complex for the simple thing im trying to do?

I'm not clear what you're trying to do. Why would you need a 12-hour timer for a curtain-closer?

 

[Jbroadway]

i want to adapt it to be a chicken coop door opener lol sorry i forgot to add that it doesnt have be a 12hr timer sorry for the confusion

 

[alec_t]

It could certainly be adapted for a door-opener. I'm guessing the relay and Q3 would need to be beefed up to control reversing/switching of a heavier-duty motor, and the motor 'on' time might be a bit longer than for curtain-closing. And yes, the whole shebang could be replaced by a micro doing switch monitoring, logic, timing and relay driving; though I doubt you'd save much in component numbers.

 

[Jbroadway]

the motor wouldnt need to be that strong it will only be a little door on a runner, i suppose it will be a better project because id be learning to program not that id have a clue how to start any of it :S if i replaced it with a relay would i not just be left with 2 relays a motor, diode, capacitor and 2 switches to tell the motor when to stop?

with a pic roughly what would i need or would i need al the transistors,capacitors and resistors everywhere?

 

[Jbroadway]

would you need two relays to reverse the motor could you simply not just use a dpdt relay like this one?from rs

 

[alec_t]

I was wondering why you wanted 2 relays. One DPCO one will be enough. Bear in mind that the starting current of a motor is much higher than the running current, so the relay contacts must be able to cope with that. Without knowing the motor properties I can't say whether that RS one would suit.
With a PIC you would still need caps, albeit for different reasons. Decoupling caps for the PIC supply are a must, and caps for debouncing the pushbuttons/switches might be needed (or they could be debounced in software). A driver transistor for the relay would be advisable, plus spike-suppressing diodes for the relay and motor.

 

[Jbroadway]

all the extra components are fine but i wouldnt know how to draw a schematics for that im new to the design side of things, i normally get my schematics online then make it.

but this time im having to design it and im really struggling? i havent done any courses or anything like that but im very keen to learn if i try and draw up a simple schematics would you be able to tell me what wrong or whats needed??

few little questions,

1. how do you get the values of the caps
2. does it matter what output/input they go into on the pic (aslong as they are i/o ports i can config them right???)
3. do i wire the solar panel into the pic also (for monitoring and switching on and off?)

many thanks

jak

 

[4pyros]

Why do you want to time the door?
Why do you want a solar panel? just for a light sensor?
Are you going to run this off AC power?
You may be better off staying with AC controls and using off the shelf controllers, depending on what exactly you want to do.

 

[3v0]

A pic needs bypass caps which are typically .1 uF between the power and gnd (close as possible to the pic VDD pin).

If you do the switch debounce in software you do not need caps for that.

But you need to know how to program a PIC.

 

[Jbroadway]

The timer is to make it automatic and is not needed if in using a solar panel and solar panel is for light detection and to recharge the battery and no it's going to be on a 6v battery