The projects brief was... Curtain Opener Closer

[MotorBoy]

Alright, so basically the project brief given to us by our DT teacher was a curtain opener and closer including use of a 555 IC, it was basically supposed to make a motor spin in one direction while there's light and spin in the other direction when its dark the output of the motor is supposed to be controllable by the values of the capacitor and variable resistor in the .

My teacher claims there is only one way of making a motor spin 2 ways and thats through usage of DPDT switches, I tried to use Op Amps and DPDT Relays but my circuit doesn't work, perhaps you guys could help point out mistakes in my circuit or recommend me some alternatives for the circuit.

**broken link removed**

 

[House0Fwax]

As a hint. Look closely at the connections to your op-amp inputs for a start.

 

[evandude]

Even ignoring the glaring issue right next to your opamp, why do you have one opamp input grounded, with a series resistor and light sensor between +V and ground there as well? And for that matter, why do you have two light sensors at all?

 

[audioguru]

The 555 has a minimum supply voltage of 4.5v. You should use a higher voltage than its minimum.
The opamp has a 9V supply so its output voltage will be higher than the supply voltage of the 555 which might blow up the 555.
Use the same 9V supply voltage for everything.

The 555 is conducting more than 200mA into the base of the transistor which might blow up the transistor because you forgot to add a current-limiting resistor in series with the base.

Why use a 555? The opamp can drive a low current relay or a transistor and relay directly.

 

[JimB]

What happens to the motor when the curtains are fully closed or fully open?
Is the supply turned off or does it just sit there stalled, and burning out?

In your simulation (what happened to REAL components?) you are using an LED to represent the motor, not a very good idea, how do yoy know when the motor is going forward/reverse/stopped?

JimB

 

[audioguru]

He uses an LED instead of a motor so that the LED lights when the motor is supposed to run forward and the LED burns out when its max reverse voltage is exceeded when the motor is supposed to run backwards.

You need to replace the battery after the curtain moves because the motor stalls at each end. Which will smoke more, the battery or the motor? Won't the smoke block the light then the curtain will reverse?

 

[HarveyH42]

Come on guys, atleast he made an effort, and posted a schematic. Lots of these school work request only ask for the solution. Got the relay part right, would add a diode across the coil for protection.

The rest of it doesn't make much sense to me. If the 555 is intended to control the amount of time the motor runs, it should be on the motor side of the relay (controls direction, not run/stop). The opamp could control the relay, but not sure how this could also be used to trigger the timer.

 

[audioguru]

Hi Harvey,
Do you think the 555 times the motor so it runs for only about 10us? Pretty small drapes or maybe the motor is way too powerful.

 

[HarveyH42]

Hi Harvey,
Do you think the 555 times the motor so it runs for only about 10us? Pretty small drapes or maybe the motor is way too powerful.

Yeah, I noticed the low values, figured I'd work on one of many problems with this circuit at a time. Didn't we have a similar project last year here last year some time?

 

[HarveyH42]

ElectroMaster should put a huge box on the open screen, that says "Before posting, search GOOGLE!'

**broken link removed**

Pretty much what was ask, and manual mode as well, even british...

 

[MotorBoy]

Alright, thanks for the comments and the website, I'll see what I can do.

The problem with the Op-Amp is, we haven't been taught the Op-amp and I had to look up what it did in the library during lunch, I guess I'll have to pay another visit there later this week.