Finished my project YAY! check it out

[Noodles141]

Ok so some of you may remember me asking for some help on circuit diagrams and stuff and well i finally finished my project i was working on and its pretty awesome, keep in mind i am 1st year haha this may not blow the minds of the experienced. Was for my electronics course at University. The project description was given to us as a mobility aid for the blind. Our idea was to put them on sunglasses that a lot of blind people already wear. We went through a lot of ideas and scrapped alot but finally came up with this idea; two LDR's on the side that sensed extreme light perpendicular to the wearers line of "sight". Small motors were placed behind the ears to alert the user when the corresponding LDR sensed light. We did this part with a voltage divider for the LDR and a simple inverter switch. We also put one on the front to sense light direction in front of the users line of "sight". This was hooked up to a 555 setup as a oscillator with the LDR dictating the discharge time of the cap. We also cheated a bit and put our beeper in backwards so it beeps once then shorts or stops beeping or something. This works to our advantage as the front LDR kinda acts as park assist but for light. the more intense the light the fast it beeps. here are some pics:
View attachment 68181Just a pic of the whole thing. a bit bulky but is ment to be a prototype.
View attachment 68183picture of front LDR.
View attachment 68184Picture of one of the sides, LDR on the right and motor on the left(it vibrates to indicate if there is light on the LDR). there is a push to make button there but only on this side. the circuit is setup with a monostable 555 setup so when this button is pressed current is supplied for a set amount of time or aslong as the button is held. this is done to save power.
View attachment 68185our control box lol very last minute since we forgot to go buy one so we made one out of thin cardboard.
View attachment 68186the actual circuit board. yes very messy but we were pressed for time towards the end and we ran out of wire so we had to make some with shorter ones thats why there is so much heatshrink haha. all in all it worked perfectly and the group i was in was very happy and we all worked hard. First university group experience and it went without a fault. Dont think many people can say that.

Please comment, will post circuit diagram if you really want to see it.

 

[throbscottle]

Well done you

 

[atferrari]

Please comment, will post circuit diagram if you really want to see it.

Please do!

 

[Noodles141]

Sorry i'ts taken me a while, was getting it from the person who had it plus my mail hasn't been working for a while. it's actually really simple how we put it together just soldering on a veraboard is a bit of a mission. We has other ideas at first that were much more complex but we couldn't get them all working together and its came down to this which is much easier and garenteed to work every time so we went with this.
View attachment 68290
Donno if you've used yenka but the max value od the LDR valued at 1mΩ is to the right instead of the left like all the other resistors.

 

[dougy83]

Wow, very fancy; needs more sticky tape though

 

[kubeek]

What is that circuit supposed to do? It looks a little strange to me..

 

[Noodles141]

The diagram is a little bit wrong, just the LDR's they are ment to be ontop of the other resistor, so just imagine swapping the LDR and resistors in the Voltage divider setup. Also their value is on the right were as all the other resistor values are on the left. The first 555, one could say acts as supply to the rest of the circuit. Its setup as a mono stable which is triggered by that little push button on the rim of the glasses. The second 555 is a oscillator with the LDR on the front dictating the charge and discharge time of the cap. while it seems the buzzer should buzz on for a while then off for a while we put it in reverse and since its a low voltage nothing goes wrong. it just beeps once then turns off, this happens every pulse of the oscillator, it kinda sounds like park assist but for light if you can imagine that. Why we put the buzzer in reverse was to eliminate the use of another 555. The Inverters each control one of the motors on either side with the LDR setup with another resistor as a voltage divider so when there is light the LDR has less resistance and there is enough of a voltage drop across the first transistor to "turn it on" and so no power is supplied to the second transistor or not enough and the motor is powered. The purpose was to have a front facing sensor to detect intensity and 2 on either side to detect direction so the user can turn and get a general idea of where the light is and how bright it is. works 100% and got my mark back. 92%, highest mark I've heard after asking a few people who were in line to do better than me.

 

[kubeek]

Powering motors and other large loads from an output of a 555 is not a very bright idea, the 555 has max output current of 200mA which you are pretty close to.
Why do you have a zener across both the motors? If they are 3.3v only it is much better to use a linear regulator to get a 3.3v rail and then switch that to the motors.

 

[Noodles141]

the motors have very low ratings. the max rating was 3.5v and i so powering it from a 555 was fine, the current never exceeds 100mA anyway so nowhere close to 200mA even. The zener was so the motors voltage never exceeded the max rating of 3.5V. just a small safety incase something went wrong since we only had 2 motors and couldn't afford to break either of them, this is the only method of voltage regulation i really know. From what i looked up the linear regulator is a another IC right? I haven't had any experience with those plus we were supposed to use what we learned in the course and they only supplied us with certain parts.

 

[kubeek]

Those 330ohm reistors will take some current on their own, but ok you are probably below the limit of the 555. But still it is a good practice to use a PNP transistor to switch on the right half of the circuit and not the 555 itself.
Or don´t switch it at all and use the reset pin on the second 555.

 

[Noodles141]

Could you do a mock of how you would do the switch with a transistor cause that was the idea i had at first, we might be thinking very differently here though. And for the second idea of scrapping the first 555, using the reset pin in the second 555 finding a way to power the rest off the output of the second 555(second being the only, scrapping the first like you say), is this what you had in mind? Just take in mind one of the criteria for this project was for it to be as power efficient as possible. So when on idle it should use as little power as possible, one of the reasons why we did it this way because this way only one 555 is powered on idle. Wanted to make a transistor switch that made is so the circuit was completely off until the push button was pressed then when a signal was sent it turned off by itself until the push button was pressed again, couldn't come up with a working idea.

 

[DerStrom8]

Nicely done, Noodles! Just curious though--how does it help the wearer again? Is a brighter light/buzz by the ear a signal that that path is open?

I love the concept. I think this might have excellent potential for future work. I recommend you keep modifying it and eventually you might have something patent-able!

Great job!
Matt

 

[kubeek]

First, look at the motor circuit, when the transistor close to the motor is on, you draw 9/330=27mA, and when the transistor is off the motor draws (9-3.3)/330=17mA. Compare this to the supply current of the cmos 555 timer, which is less than 0.5mA.
If you want it to be energy efficient, you should have a look at the transistor arrangement that drives the motors. I will try to draw someting, what transistors do you have at hand?
Also, what is the resistance of the LDR in shadow and in light?

 

[kubeek]

Ok, so I think that you will be much better off if you connect the motor like this:
+9v - 6v zener - motor - collector of transistor - emitter of transistor - ground. This way you won´t be using the 27mA when the motor is off. You want the motor to turn on when you shine light on it, right?

 

[Noodles141]

ya turn on when it shines, and i think i get what your saying. Never though of it that way. That would actually be more efficient. The transistors we were supplied were cheap, donno the model or anything, don't even know if they were npn or pnp cause they were crammed in small boxes, they were labeled npn. And with that 6v zener. That prevents the extra 6v from travelling trough the motor right. also what about the transistor gain, wont this effect this circuit or not. Why do you say that the motor draws 17mA when its off, dont understand why it would. also the 555's we had drew 5mA when idle not 0.5mA maybe a just the make or am i confusing that 0.5mA u stated with some other rating.
ps
if you got an email and it was me saying kinda the same crap as i did in my previous post, i didnt see this had gone to a second page *facepalm* though my post didn't go through

 

[Noodles141]

@DerStrom8
Sorry only your comment now. Its targeted for blind people who has 0 visibility, there are blind with a small range of visibility that can see glimmers of light in a room and kind of tell where it is coming from. The objective here is to help someone with 0 visibility to have that little advantage that others with close to 0 visibility have. The front is an intensity sensor and the sides help tell if there is light perpendicular to the persons field of "view". So in fact they would have an even bigger advantage over those with close to 0 visibility cause the sensors can detect more that 180 degrees around the persons head. With the intensity the wearer can find out how bright the light source is and with the ones on the side he can find light around the room more easily with out having to swivel ones head around to much, the point being to find where a window in a room is or a door if there is enough light coming from the door. And yes when there is light a small vibration is felt on the temple for the corresponding LDR detects light. So no light means no buzz or vibration. light means a buzz or vibration.