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Well, I have an analog alarm clock, which simply beeps at a given time. So I opened it up, removed the buzzer [...]
[...] and connected the two wires to my multimeter (as I have no access to an oscilloscope). I saw that the reading alternated between 0V and around 0.250V (on the d.c. reading). What does this mean?
I want to straighten out this voltage, and use it to 'turn on' a transistor; the transistor will then turn on a 3V d.c. motor. I plan on using a 9V battery as the power supply.
I think I would need the motor to stay on as long as the clock gives the d.c. signal.
My questions regarding this are:1) Can I simply use one capacitor to straighten out the d.c. wave? If so, how do I know what capacitance to use? If not, how would I straighten it out?
2) What type/make of transistor is appropriate for this?/How do I know which one to choose?
3) How should I connect the whole setup? A schematic would be helpful, but if not I can understand. I have some basic knowledge of electronics (though I'm still in high school) and I do know, as an overview, how transistors work.
By "buzzer" you mean...?
Is there a coil near the buzzer?
If the voltmeter is True RMS, the 0.25V will be the average voltage of the waveform, if it isn't, all bets are off, but likely a 'scope would reveal a low duty cycle signal of several volts.
Try something like an 1N4148 diode from the output (cathode) to a cap (anode) of eg. 100nF (with the other end of the cap to ground) and measure over the cap.
Why would you want to drive a 3V motor with 9V - do you carry a grudge for this motor?
You think? Well you better be a little more certain before you start building, as that choice influence how it should be done
How did the buzzer sound - a continuous tone of a certain frequency, an intermittent signal (like beep-beep-beep) or what?
That cannot be answered without knowing the motor current.Measure the motor current when running at 3V and with the intended load.Don't try to run it at 9V!
...place a reverse biased diode over the motor terminals, or the transistor will die soon.
If the signal is intermittent, you could use it to either trigger a 555 directly, or use a 555 as a missing pulse detector, to give it a constant output as long as the signal keeps going.
I'm not entirely sure what type of buzzer it is; I took two photos which I hope will help identify it:
No, as far as I can tell the only coil in the entire clock is the one that is connected to the second hand.
Hmm.. Well we do have an oscilloscope at school. Do you think it's necessary that I ask permission to borrow/use it?
When you say the other end of the cap should go to ground, you mean it should go to the anode of the 'buzzer' yes? (The buzzer, by the way, does have + and - markings on its terminals) It's because I haven't yet disconnected the buzzer from the wires..
Haha, of course not. It's just that I found a 3V motor which is the perfect shape and size (I believe it's a CD-player motor) for my purposes, except the torque isn't high enough at 3V. Which is why I had planned on using a 9V battery as the source. But now I think I'll reduce the load and test it again at 3V. Would it still be bad to the motor if I gave it 9V say for 2-3 minutes (not in one go) per day?
I only said "think" because I didn't want to seem too demanding by saying "I want this.." But yes, I do want the motor to stay on as long as the clock gives the signal.
Quote from: Soeren on October 30, 2011, 09:04:24 PM...place a reverse biased diode over the motor terminals, or the transistor will die soon.I understand that this is necessary, but would you mind explaining to me why? Also, why does the diode have to be reverse biased (which I take it means it is connected the opposite way)?
I was in fact also thinking about using a 555 timer, but I'd like not to go down that path as far as possible - If, however, I do end up needing to, I'll have to do some reading up on the timers first, since I've never used one before.
No, to the negative terminal of the buzzer, like this:Try it without disconnecting the buzzer at first, then you'll know when some voltage should be on the cap.What does the voltmeter reveals with this circuit?
9V batteries doesn't have much capacity and a relatively high internal resistance, so will be a poor choice for this. 2 (or perhaps 3) AA cells would be a more sensible solution.
Approximately how long would you guess the pauses between the beeps to be?
This also explains why it's reverse biased (when the motor is running, it shouldn't conduct, or it would short out the motor).
That you haven't used them before might be a very good reason to get your feet wet in a controlled way. I can draw you a schematic, so it would just be putting it together and perhaps measuring a bit.While what you need can be made with transistors, going for a 555 solution would give a neater circuit and would probably make you want to experiment a lot with this multi-purpose IC.If you feel like dipping into the 555, I'll recommend Tony's Tutorial, as it is quite digestible if you don't try to take it all in in one go.
I'm going to try this in a little while (I seem to be all out of diodes) and I'll let you know what it measures. However, I have another question: why is the diode necessary? I mean I understand that it rectifies the signal, but I thought that was only for a.c. signals - that it would allow the positive voltages to go through but not the negative. Did I have a misconception of diodes? Because clearly here the signal from the clock PCB is a d.c. signal..
It beeps really fast, but if I had to make an approximation, by looking at the second hand on the clock, every second something like this happens:[...]So continuously, there are four beeps with a third of a second's gap in between the set of three. The time between two beeps is tiny.
Yes, I would be very grateful if you could draw up a schematic for me. Also, to aid my learning process, could you briefly explain what is happening at each stage of the circuit? Thanks
And I just read through that website you sent me. I think I have a conceptual understanding of the timer now, though I'll have to go back and study it again, as the explanations for Pin 2 (Trigger) and Pin 3 (Output) completely lost me
It's a pulsating DC and if you added just a capacitor it would charge and discharge with the signal, only delayed a bit by the RC filtering, where the output impedance would be the "R" and since it's very low, the cap would follow the signal pretty closely and you wouldn't have gained anything.
So, to recap, the max. time without sound in the time span where the motor should be running is around 1/3 second?
Sure, but I'll need the value of the peak voltage from the clock and the motors current consumption with the load attached (at 3.0V or 4.5V).
Nobody can grasp each bit of that amount of information in the first go, but it helps to study fig. 3, with the two comparators referenced to the voltage divider (the 3 x 5k resistors) that gave the chip its name.
Exactly. If you like I could take a relatively low quality video showing the clock 'in action'...
I set up the circuit as in the schematic you posted earlier, and my multimeter, set on the d.c. voltage setting, read about 5V, give or take a few hunded mV. It fluctuated between that value and close to zero, in pretty much the same timing as earlier, without the capacitor or the diode.
I was just getting around to measuring the motor's current consumption when I ran into a mechanical problem - the 'blades' attached to the motor (basically its load) fell apart and right now I'm working on fixing that. But I will try to give you the current consumption as soon as I can.
would using a 555 timer make the circuit be classified as a digital one? Not that I'm against creating a digital circuit, but I'm just curious.
...so let's save it for if the circuit acts up.
So, it's a "fan alarm" you're making?
I wouldn't call the entire IC digital.
So, I made another circuit, with no current drain except whenl the alarm signal drives it and the circuit just awaits the motor current measure to get the output drive right and I can post it.
Don't think it's a waste to learn about the 555 though. It's a chip with a multitude of applications.
No, not exactly. I'm making more of a "water alarm" - the motor drives a pump which is meant to spray water in my face.
I thought of making it because 1) I have huge problems waking up early for school and
2) Simply because I wanted to make something electronic and functional.
The pump basically works on principles of air pressure; the motor has blades attached to it and is inside a small plastic can - when the blades spin, the air pressure is reduced and water is sucked in from the bottom end of the can, which is immersed and has a pipe attached to it. The water is then passed through a longer pipe, which ends at a small 'shower head' conveniently hanging over my bed
The problem I'm having is that the blades keep falling off - I've tried hot glue, super glue, rubber cement. I also found that the pump isn't very powerful this way.
Not completely relevant, but would you happen to know of any alternative ways of pumping water? I think I got the idea for this pump from Instructables..
I know that "digital" means discrete values and "analogue" means continuous ones - so would ANY circuit that has a programmable chip be considered digital? And would any circuit that does not have programmable parts be considered analogue in general?
I will fix the mechanical bits of my project and get back to you on the motor current within the next few hours. *crosses fingers*
Quote from: TheDarkLord on November 01, 2011, 05:55:22 PMI thought of making it because 1) I have huge problems waking up early for school and I think it's a general problem among experimenters and I'm sure you know the real cure for that one (and I don't mean dropping out of school)
If only I followed my own advice...
Not knowing what exactly you want to join, but you may consider some two-component epoxy glue (Araldite or similar) - it's good for a lot of materials.
There's plenty of ways to shave that goat, but I assume you don't wanna build it from raw material?
Perhaps a gravity feed with a solenoid valve would be a better way to go. Install a tank/bottle up high with a tap and have a solenoid valve open. when you need the shower.
Flashing a bright lamp (or high power LED/LED cluster) pointed towards you at up to 10..15Hz will reach your brain through your eyelids and eyes, possibly forcing your brain waves into a rythm that wakes you up.A vibrating motor in a box tucked under your pillow (used by many deaf people).One of the more radical (even worse than water) ideas was posted in a magazine some 20 years ago, aimed at lucid dreaming triggering. It was a shocker circuit with two electrodes mounted on a leg and pumping the battery voltage up to some hundred volts of AC - quite effective, but not a good first (or tenth) project for safety reasons of course.A mechanism dropping ping pong balls on your head might be sufficiently annoying as well.
Don't loose any sleep over it
The real cure.. Not experimenting? In that case I don't think I'll ever be cured
Well, you certainly seem to have picked up enough to help yourself and others I really appreciate all the help, thanks!
I managed to fix it - still using hot glue, but now made the 'blades' out of aluminium from a soda can;
the curves really help [...]
No, I'm afraid you assumed wrong - I did want to build it out of raw materials, because otherwise the mechanical part of my project would be very little and I really do need to improve my 'mechanical' skills
I thought of that, but again it seemed too easy; I did want a bit of a challenge to keep me engaged.
Haha, I like that last idea! Maybe once I get into the habit of sleeping with a towel and start drying myself off after the alarm to go back to sleep I also like the idea of the LED cluster - maybe I could develop into that when I finish with this.
Well, after pulling two all-nighters (sarcasm) I finally managed to finish it, and I must say, running the motor for 10 seconds with a 9V battery, it works even better than before. I'll post a video when I've finished the electronics too. Right now I'm waiting on some AA batteries, since I'm apparently all out of new ones - so I can now safely say the current reading will be present in my next post!
I got readings of 30-40 mA without any water present between the blades of the motor. After adding water, the motor drew a current of around 197-199 mA, and at times it went even higher than 200 mA - my multimeter can only measure a maximum of 200 mA of current.. Oh, and I was using 3 AA batteries (1.5V each) connected in series as the power source; the batteries are brand new.
Hope this isn't too late, and that you can still help!
No, I meant getting to sleep an hour or so earlier
Heh, you've got to post a photo of that contraption Judging from your time zone, you're either in the US or somewhere in South America, but this sound more like how they'd do it in Africa, where soda cans and beer caps is turned into whatever - sometimes with great ingenuity.Hmm. "aluminium" is how we spell it this side of the Pond... Where do you live?
OK then, I was more thinking in terms of what tools are available to you. if you have access to a drill pre4ss, a lathe and perhaps a mill - and chunks of brass or aluminum, you can make almost any kind of pump, but i didn't get that impression?
When you want to learn, a challenge is great, as it force you to think laterally.When you need to make something that works reliable, the less challenges, the better.
OK, I changed the circuit to 6V to give the motor a bit more push. If it gets hot in use, back down to 4.5V or use some 1N400x diodes in series with the motor to lower the voltage.
Nah seriously, why would it be too late?I got an email recently, going something like "I got a new car, how could I change the circuit to work with that" - turns out I made him a design around 5 years back - a circuit for controlled re-fueling (en route) when driving with a caravan, but this guy expected me to remember all the details from around a thousand designs and a couple of PC's back and the files might not even exist anymore (real men(TM) doesn't do back-up They just cry when everything is lost ). Luckily he had kept the schematic, so I managed to reconstruct it (it was a quite elaborate analog controller, as he was allergic to digital design).Turned out it wasn't too late either, although it took me a while to re-enter the thought process of when I originally made it.
I made it into this .PDF-file complete with PCB layout and circuit explanation.If it acts up, just complain
Haha, well it does help to be "material-smart" - the end product does not always look professional, but it functions decently. I actually live in Mexico. I take it from your name that you're of Scandinavian origin, perhaps from Denmark? How come you've come about to have so much knowledge on pretty much everything?
No, well I don't have access to any power tools, but I was thinking more along the lines of building a pump out of raw materials that I can find around the house - for instance I used a plastic film canister as the pump housing.
All right.. but does that mean I need to measure the current again using 4 AA batteries?
What's amazing is that the person still remembers you!
1. Is it important what resistors I use? Would it make a difference if I use the carbon ones as opposed to the metal film ones?
2. Is the capacitor an electrolytic one?
3. The shop from where I usually buy all my components doesn't seem to hold the BD140 transistor (Q2) so what would a suitable alternative be? It doesn't matter if there aren't any alternatives; I could go into the city and they have hundreds of component shops all lined up, at least one of them would have it
4. Should I disconnect the buzzer from the terminals now?
Yes, I'm a Dane and living in Denmark (well googled )
Perhaps you should start a web site dedicated to "recycling techniques"?
Quote from: TheDarkLord on November 04, 2011, 05:27:38 PM2. Is the capacitor an electrolytic one?Yes.
TIP42 springs to mind, but any PNP transistor able to handle at least 1A and having a current gain (hFE) of at least 40 should do.If you tell me what they have, I can point one out - do you have web links to any of the shops?
Only if you want it silent, but it shouldn't matter for the function.You could add a louder alarm if needed (if if your family can bear it )
Googled? No. I actually used to live in Sweden, and came across a few people with the same name as you, and I think most of them were Danish.
And on the .pdf it says the cap is rated for 10V. Would I be fine using one rated for 16V?
That's all the transistors they have. But like I said, if there aren't any suitable alternatives, I can go to the city and they're very likely to have it there.
Alright! Thanks again, I'll try finishing the circuit by this weekend and let you know how it all goes
They do have the 45V BD136 (the BD140 is 80V), and that should do.Alternatively, there's the TIP32 that can handle twice the current. It's unclear whether it's a 40V or a 60V version, as they write 40V on the page, but TIP32A which is a 60V version, but both would work.
They sure seems expensive though. Denmark is very expensive with components, but I can get a BD136 at around $1.20 locally - I'm sure you can get at least 5 for $1 at eBay.
It would be gold if you could set up a video cam to start right before the shower hit you and the next few minutes onwards
Really? I don't find them that expensive. Oh wait, maybe it's because you're confused with the dollar sign. The prices on that site are not in U.S. dollars, they're in Mexican pesos - many people get confused since both currencies use the "$" symbol. 1 U.S. dollar is about 13 Mexican pesos, so I'd say they're quite affordable.
Ah, now that that idea has entered my head, I'll find a way to do it Though when it comes down to it, it might just be easier to fake sleep and record it..
Well, I fully understand if you'd like to keep such a moment to yourself - I know I would
Well I put together the circuit on a breadboard...and it doesn't work.
So I started checking voltages with my multimeter and found that there is a fairly large voltage going into the BC547, but apparently a much smaller one coming out of it.
Could the transistor be defective?
I've tried replacing the 330uF cap with a 470uF one but still nothing.
I did notice that when I removed the capacitor, the motor gave off a tiny, almost inaudible beep similar to the buzzer.
I also noticed that the collector of the BC547 (Q1) goes to Q2 while its emitter goes to ground. Why is this? Shouldn't it be reversed? (And by the way I did try reversing it - still nothing)
What could I try now?
OK, is it a solder-less breadboard?
If you have your voltmeter at the collector of Q1, it should be close to the battery voltage and when the buzzer beeps, it should be close to ground (less than 0.5V).
First, you didn't swap the Buzz- and Buzz+ by chance?
What's the voltage from ground to the top of C1 when it beeps?
Then touch the positive input (K1, pin 1/Buzz+) to the positive side of the 6V battery (K2 pin 1) Does this get the motor going?
If not, measure each resistor, to check if they're what you think - it's sometimes hard to tell some colors apart (like orange/red, brown/red, brown/violet, green/blue).
Yes, I actually wasn't aware that there were breadboards you could solder to.
Quote from: Soeren on November 07, 2011, 03:26:21 PMIf you have your voltmeter at the collector of Q1, it should be close to the battery voltage and when the buzzer beeps, it should be close to ground (less than 0.5V).Just tested that, and it's how it's supposed to be.
I take it that is the same as the voltage across C1 when it beeps? Well it varies from around 0.9V to 1.1V.
Quote from: Soeren on November 07, 2011, 03:26:21 PMThen touch the positive input (K1, pin 1/Buzz+) to the positive side of the 6V battery (K2 pin 1) Does this get the motor going?Yup, it runs like a charm with the buzzer input removed.
I noticed that by removing R4, which connects the base of Q2 to +6V, the motor runs almost perfectly as I want it to - save for the fact that the motor runs in bursts of spin-slow down-spin-slow down. But I think I could just try a higher value capacitor value since you said that is what affects the timeout? My question is, would eliminating R4 have any effect on the circuit, e.g. blowing a transistor or something?
P.S. Sorry for the delayed post, I've been a little caught up in school work all week.
A breadboard can be just about anything, from a wooden board with brass/copper nails, an unetched PCB that you glue tiny bits of the same to for soldering pads etc.The solderless boards can be a pain with certain circuits, especially when they're some years old.
Quote from: TheDarkLord on November 12, 2011, 11:09:27 AMI noticed that by removing R4, which connects the base of Q2 to +6V, the motor runs almost perfectly as I want it to - save for the fact that the motor runs in bursts of spin-slow down-spin-slow down. But I think I could just try a higher value capacitor value since you said that is what affects the timeout? My question is, would eliminating R4 have any effect on the circuit, e.g. blowing a transistor or something? Good thinking and trouble shooting!You cannot rule out R4, as it is used to pull the base of Q2 high when the buzzer is silent (to keep noise and radio signals from opening Q2), but it can be made larger.
Yes, a larger cap will get rid of the intermittent running (as long as the alarm clock fills it)
Quote from: TheDarkLord on November 12, 2011, 11:09:27 AMP.S. Sorry for the delayed post, I've been a little caught up in school work all week.Don't be, your project is mostly for fun I assume - school is for life!
And before I forget...R2 1k (to 1.5kR3 10k (to 20k)R4 10kR5 100RR4 is probably the most important, then R3, but changing them all should more than make up for Q2's low gain.
Thank you! I'm not sure I understand how noise/radio signals would open Q2.. Care to elaborate please?
Up to what maximum value would it be safe/wise to try?
EDIT: I just put it all together with the new resistor values - and with a higher capacitance - and it works perfectly! I'm feeling on top of the world haha. Well thank you so much, I can't sufficiently express my thanks in words! I'm so glad you could help me, thanks again! By next weekend I'll solder it all on a perf. board and maybe post a video here on SoR, I'll be sure to show it to you as well!
Quote from: TheDarkLord on November 12, 2011, 01:48:31 PMThank you! I'm not sure I understand how noise/radio signals would open Q2.. Care to elaborate please?The floating base will act as an antenna, although the one you have doesn't appear to be very sensitive, but it's a cheap insurance. A lot of people building sensitive amplifiers end up with what is generally called "Radio Moscow", which is when a radio station (or more than one) breaks through the sensitive front end. "Radio 'Moscow" on Q2 wouldn't be sound of course, but rather a little tingle of water here and there The higher the input impedance and the higher the gain of the device is, the more important it is to keep the base in check at all times.
Quote from: TheDarkLord on November 12, 2011, 01:48:31 PMUp to what maximum value would it be safe/wise to try?The only safety concern would be whether the alarm output would be able to drive it without getting shorted, but R1 takes care of that, so the sky is the limit - it shouldn't be needed though.
'Then you're ready for trying with light
What would I need to change in the circuit so that the motor turns on and spins for a set period of time when the alarm rings (let's say 40 seconds) before it turns off by itself regardless of the length of the alarm tone?
Using a 555 timer perhaps?
A non-retriggerable monoflop (MF), which is not able to start a new timing period, until the signal have been returned to the resting value.A retriggerable MF, when timing out, will either retrigger or just keep its output active, if the input signal is still active.
I have attached a new schematic with 2 alternative output stages. The first uses the transistor you already have and can be used with a CMOS-555, which will ensure that it works all the way down, while the battery discharges.
The regular 555 will cease to work before the battery is run down all the way (to 0.9V/cell or 3.6V total), but since there are differences between the versions from different manufacturers, I cannot say at what voltage your specimen will give up.The CMOS version will work all the way down (it's guaranteed to work at a voltage as low as 1.5V).However, the CMOS version is expensive compared to the regular version, so you decide - no harm in trying the cheap one, as long as you test how far down it will work.
If you haven't got a 1M trimmer resistor or don't want it to be adjustable, use a single resistor of around 820k for VR1 and R6 to get roughly 42s - that said, you might need to experiment a bit, as electrolytic caps have wide tolerances. The formula for the timing is: 1.1*Ct*Rt = 1.1*C3*(R6+VR1)Plugging in some numbers: 1.1*47µ*820k = 1.1*0.000,047*820,000 = 42.394s
Wishing you a nice cold morning shower (Later you could add a circuit to automatically call in sick to your school, if you sleep through all 40s of that).
what exactly is a monoflop? A component or a type of circuit?
When you say "while the battery dicharges" does that mean it will discharge if I leave it plugged in overnight? Or just "discharge" like in the long run?
What type of 555 timer is this? It doesn't actually specify.. but judging from the price, could it be the regular version?
If I'm not mistaken, a 1M trimmer resistor is a potentiometer of the same value?
Which of the first three products on this page would be the most suitable?
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Mechanics and Construction