All About Circuits Forum

Brother USB label maker on sale

spinnaker — Fri, 20 Nov 2009 21:26:34 GMT

I happened to stumble on to this great deal today.

It is normally a $49 label maker but it is on sale at Jt for $24.95 plus free shipping.

I just ordered one myself.

I figure most people like to make labels for their projects, so thought you would all want to know about this sweet deal.

Moderator's note: Consider contacting the OP by PM about this sale if you are interested.

Motion activated TARDIS oscillating light and sound effect

jugglingguy — Fri, 20 Nov 2009 21:10:30 GMT

Hello all,

I am brand new to circuits and wiring, but I have been given a task that requires me to learn some. I need to make a card box for my brother's wedding that looks like the TARDIS from Doctor Who (about 2 feet tall). Cards will be put in through an ajar door, and the card needs to trigger a switch that causes the light on top of the box to slowly strobe on and off while playing the sound of the TARDIS landing. It only needs to last approximately 10 seconds.

Preferable this will run off batteries, but I can deal with having to plug it in if necessary.

So far I have found this potentially for the sound effect. I have looked at both PIR sensors and Ultrasonic for the initial trigger, I'm not sure which is better (the cards might not be warm enough to trigger PIR?).

I have not been able to find a circuit that will slowly strobe a small bulb. The only restriction for the bulb is that it needs fit inside a cylinder 2 inches tall with a diameter of 1 inch.

Any ideas would be greatly appreciated. When it's finished I'll get pictures and video up to show how it worked!

PS The sound effect can be found here. And this is the TARDIS (for those sad people that don't know)

electronic circuit for bio medicine practical engineering

joni — Fri, 20 Nov 2009 20:47:25 GMT

I search after electronic circuit for heart pulse meter
also I search after electronics circuit / codes for small project in computer vision for bio medicine practical engineering or /and network communication application for bio medicine practical engineering or other electronic circuit that connected to bio medicine

Voice effect

TheBellows — Fri, 20 Nov 2009 20:45:01 GMT

Hey, i'm kinda noob at this, but i made this circuit and it sounds kinda cool except for the continous oscillation in the background.

Are there any simple ways to filter or gate away the annoing tone?
I've tried to filter it away with some caps and some resistors here and there, but with no acceptable results...

Are there better ways to acheive this sort of voice effect?

Attached Images

voce-effect.jpg (69.3 KB)

about cat tracker

dmsmith — Fri, 20 Nov 2009 20:34:54 GMT

In 1987 i built a small tracker use BF224 RF transistor as a sqegging oscillator,
1t was just over an inch long and slightly bigger in diameter than an SR44 button cell. It had range of approx.,80 meters line of sight on level ground with the osc.,4 inchs above ground level,and relying only radiation from the osc., coil.This little device worked well for 13 years with battery change every 6/8 weeks until the cat died.
In order to get suffecient amplitude from the sqegging pulse i had to make simple AM rec., with a bandwidth of about 2 mhz.Now that i need to use the device again i find that because of the bandwidth of the rec.,the range has become only 20 meters, due to what i think are spread spectrum transmmisions.
A transmitter is needed useing more up to date components,and possably a minature xtal for freq.,stability.Can anyone help?
dmsmith.

12V Time Delay Turn Signal for Car

Slantsixx — Fri, 20 Nov 2009 19:38:52 GMT

Simply put, what I am trying to do is modify my car's turn signals so that when the turn signal lever is activated for more than about 400ms it will act normally and cancel as soon as the lever is released, but if it is activated for less than 400ms or so, it will activate a time delay so it will stay on for 3-5 flashes.

I do a lot of highway driving (lots of drive right pass left) so I change lanes a lot. I've seen some newer cars with this feature where you just momentarily move the turn signal lever and it will flash several times, but if you hold it then it operates as normal; so I want to replicate this in my car.

I've looked into time delay relays, but as far as I can figure out, that solution would mean the turn signal would stay active for a given amount of time after the lever is released all the time, not just when momentarily activated.

I have basic electrical knowledge, and virtually no electronics knowledge, so I don't know if there is some sort of relay(s) to use, or if a microcontroller would be a better solution. I have some programming knowledge so figuring out that part shouldn't be too hard, I just need to know the best route to take on getting there.

My current flash-regulator rate fluctuates with voltage, and it's an older car, so the voltage goes around between 12-14.5V and the flash rate is all over the place, so maybe I could kill two birds with one stone and use a uC to also regulate the flash rate as well.

Reading up on some different uCs, it seems like it should be fairly easy to accomplish what I am trying to do, but I still can't figure out how to get the time delay to operate only when the turn lever is active for the given period of time. (with a 50-100ms lower cut-off to prevent the opposite side time delay from engaging when the lever returns).

I'm a poor college student, so cheaper solutions are better solutions even if it's more difficult; I like a challenge ;)

My Transmission Line dissertation

KL7AJ — Fri, 20 Nov 2009 19:33:51 GMT

Actually, this isn't a dissertation, but rather an appendix to the Opus of Amateur Radio Knowledge and Lore. For anyone interested in the history and background of transmission line theory, I think you'll get a kick out of this.

Eric

Attached Files

Ladder Line to Eternity.doc (74.0 KB)

superposition and nodal analysis

studentofcomputerscience — Fri, 20 Nov 2009 19:18:02 GMT

Hello :-)!

I've got simple exercise about nodal analysis and superposition. I need to use these two methods in order to calculate current i1. My attempt is here: http://i50.tinypic.com/nq3e45.jpg . Unfortunately results from both methods are different. I guess I took current source into account in superposition method improperly. Can anybody tell me, please, what is wrong with my solution? (The second required thing is to calculate powers in this circuit).

Thanks for help in advance!
Greetings!

ID Inline fuse on a box fan

Gdrumm — Fri, 20 Nov 2009 19:01:57 GMT

I'm working on a cheap Galaxy Box Fan that stopped working.
I have found what I believe to be a small blown fuse, inline with one of the power feeds.
I tried to find it on ALLDATASHEET, but came up blank.

It looks to be ceramic, about 1/2" long with brownish gold lettering, and brownish gold tips on either end,. The info includes:
E
115 C 2A
M N110
069

Continuity test was negative (no conductivity).

Have I identified this correctly, is it a small fuse?

Thanks,
Gary

Question about temperature dependence of Battery capacity

steveb — Fri, 20 Nov 2009 18:53:05 GMT

I have a battery question that has proved difficult to answer. Apparently it is a tricky question because consultation of over 30 research papers, a 1000 page battery book and questioning several engineers has not revealed the answer. This, despite the fact that it's basically a very simple question. I have a high regard for the depth of knowledge and deep-thinking ability of the people here, so here goes!

First, here's a statement of well-established fact. It is known that the maximum battery capacity (i.e. AHr rating) increases as temperature increases (within reasonable operation limits, of course). This means that a warm battery is capable of storing more energy/charge, compared to a colder one.

This leads to my question.

If you have a colder battery that is fully charged to it's maximum capacity, and then heat it, will the battery have more usable energy, or the same energy? In other words, will the battery still be charged to its (now higher) maximum capacity, or will it now be charged at a capacity less than it's new maximum value? In the second case, you would then need to charge the battery further to take advantage of the higher capacity, while in the first case, you would damage the battery if you charge it further.

I have come up with my own unverified answer, based on logic, but I need a real answer and a scientific explanation of why it is true. My own thought is that a fully charged battery stays near it's maximum capacity as temperature changes and the stored energy goes up and down as temperature goes up and down. I say this because otherwise a battery fully charged at room temperature would be damaged when cooled because it would then exceed it's maximum allowed charge. However, I'm in a situation where guessing, even if rooting in logic, is not allowed.

The basic reason for my question is that I'm making an equivalent circuit model for batteries based on what is available in the literature. I've now found several usable models which include temperature dependence, but seem to predict that capacity changes with temperature, but stored energy does not change with temperature. In other words, it contradicts my logical argument above.

Help with a Resistor Cube

jpmillet — Fri, 20 Nov 2009 18:20:28 GMT

I need to use the node tension method to find the resistance in the traditional resistor cube. Please its for my university class, im from Mexico. Hope someone can help.

what if i dont use the RFC!what will be the result!

aj_silverthunder — Fri, 20 Nov 2009 17:27:18 GMT

guys tell me what if i don't use the RF choke in this circuit,will the transistors,capacitors,etc.. get burned out or else what will be the result!~

Attached Images

30wvhf.gif (9.5 KB)

Starting a project - Transistor problems

Excizted — Fri, 20 Nov 2009 15:07:40 GMT

Hello all. I've just started my first real electronic project, and therefore I've come to this forum :)

I'm trying to achieve volume controlling from an Arduino for an external sound device, and I've been searching like a mad man.

What I guessed would be the easiest way to do this was to use a transistor and wire my sound source, sound destination and a analog output from the Arduino.

This does not work as it is supposed to. When I send analog signal 255 (max of 5v Arduino) the sound start flowing, but when decreasing it to 180 I'm not able to hear any lower in the sound. I guess I'd just turrn it more down, but anything under 150 simply means no sound at all.

What could I be doing wrong, and is it at all the right way to go trying to manage volume from a second signal?

Thanks,
Excizted :)

TLC272 Substitute

keithg — Fri, 20 Nov 2009 13:38:49 GMT

I need a voltage sensing window comparator opamp subsitute for TLC272. Would you please advise an alternative. An LM386 will provide input from an electret mic. The application is a noise monitor for our elementary school cafeteria. Thank you.

The lowest operating temperature for a Diode

Abel Assegid — Fri, 20 Nov 2009 12:32:12 GMT

Hi Everyone, I can any one tell me what could a diode,s minimum operating temperature be? From the dustsheets everywhere all I see is the maximum junction temperature.

Or can I assume the minimum storage temperature to be equal to the minimum operating temperature?

Thanx.