audioguru

Mixos, thanks. I will double-check the index page when notified (since I am sent to it anyway) to see if it reports me as making the last post in that whole index. Perhaps you misunderstood my 2nd concern: Having the e-mail notification linking directly to the last-posted message of a thread would be good, but not necessary. I was hoping that the notification could directly link to the general thread, instead of to the index page as it does now.

Mixos, I always want notification of replies to my posts. But frequently I get e-mails about replies, then I have to go there to find that the reply was the one that I just finished. Can "notify of replies" exclude my own reply? The "notify of replies" e-mail shows the thread, which is good. When I open it, I am sent to the index, not the thread. Can the e-mail link directly to the thread? Thanks ;D

Mixos I just now got that same error, twice. It has more information for you: Warning: file(): php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution in /home/electronics-lab.com/www/footer/linkman_0.php on line 30 Warning: file(http://www.electronics-lab.com/footer/linkman_0.php?mode=links): failed to open stream: Resource temporarily unavailable in /home/electronics-lab.com/www/footer/linkman_0.php on line 30 Warning: join(): Bad arguments. in /home/electronics-lab.com/www/footer/linkman_0.php on line 30

Mixos, Thanks for fixing the Fatal Error. Now (last 24 hours) I am getting this new error each hour: An Error Has Occurred! 2: file(): php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution (/home/electronics-lab.com/www/footer/linkman_0.php ln 30)

Do we have ANY projects that work properly? (2 inverters, 30V power supply, stethoscope, IR detector, 6-channel disco lights, batteries charger, roadrunner, etc. and now this one). The authors of the above claimed that their circuit works. I had fixes for them all.

Ante, JLB's constructed project does not work and he believes (as I do) that the circuit cannot dim its LED. If the dimmer knob for your car's dashboard didn't work, wouldn't you complain and wonder why-not? Your eyes' response to light is the same as your ears' response to sound: Logarithmic. Double the lights and it is just a little bit brighter. It is the same with audio amplifier power, 20W sounds just a little bit louder than 10W (only 3dB difference). 10 times the light looks twice as bright and 10 times the audio sounds twice as loud. Since the LED in this project is operated at just 1mA, even though the author doubled the LED drivers and duty-cycled the on-time, then 10mA (if possible) would look more normal.

ZomBiE, Your Commodore still works, great!

This attenuator reduces the speaker or earphone level from the scanner to the microphone level of the recorder. Use shielded cable.

Designing another circuit? No. Just add one capacitor. That will fix JLB's complaint. Replacing several other components? No, the opposite. After replacing IC1, eliminate D1 and R2. Replacing the main IC? Why not? Most of the original ICs don't work with new batteries and they all won't work when the batteries are running down. The replacement IC is the same, but improved. Pseudo PWM, cancelling operation and duty cycle? Where? The oscillator has a permanent 90/10 duty cycle only so that the LED is brighter (it gets only 1mA). Theory? JLB saw it, I see it, why can't you see it?

Kasamiko, What are you using 330VDC for? That's enough voltage to glow in the dark!

Electrodoc, I am glad that the modified circuit works well. Additional modifications: 1) It will probably be even better with the 100Hz cutoff bigger capacitors. 2) As I explained in your other post (Theory), the additional filter cap across RV1 operates poorly because the low input resistance of the T2 stage loads it down. It works much better with the volume control turned way down. If you replace T2 with a high-input-impedance darlington transistor, and change R4 to about 330K, then this filter cap will work well at any setting of the volume control. 3) Of course the filtered circuit will still respond to loud voices since the simple filter has only 2-stages, and the voices may have frequencies in, or near, its pass-band. An 8-stage, switched-capacitor filter chip could be added, but may not give much better results. 4) Changing the microphone type won't make any difference. 5) Your audio tone-control circuit is designed to gradually boost or cut frequencies below (for bass) or above (for treble) about 1KHz, so won't work for just the beat. Even if it was modified to boost below 100Hz, it won't make much difference because it has only a 1-stage filter.

Believe? Isn't the LED driven by a logic gate (actually 2 paralleled to get more ouput current)? Can't you see that the output of a logic gate is either high (LED off) or low (LED on) but never in between? This gate is a Schmitt trigger, so even feedback (which the circuit doesn't have) won't make it linear. There is no way that this circuit can dim the LED without Pulse-Width-Modulation, that it doesn't have, yet. The author of this project states that the signal at the probes alternates, in order to eliminate a plating action at the probes which would be caused if the probes had DC (or assymetrical AC). But the original circuit uses assymetrical AC (causing probe plating) so that the LED is on most of the time (PWM) because the standard CMOS driver has a very low output current when operating with a 3V supply. The 74HC132 which I propose using, is a quad 2-input Schmitt trigger Nand gate which is guaranteed to operate with a supply voltage as low as 2.0V. It has much more output current. It can deliver a perfect 50-50 signal to the probes and still have enough output current to drive the LED brightly when required. Why a 3V supply? A single lithium cell, 2 AAA or 2 AA cells are more compact than a 9V battery and will last 10 times as long.

Kasamiko, Congratulations for finding it. We call low line voltage "a brownout" over here. Now you can build an Uninterruptable Power Supply with a nice big inverter inside. When the line drops or fails then the UPS continues the power.

MP, You made an incorrect statement: "nor is it a gated action which turns on the LED". Of course it is gated action, the LED driver is a Nand gate (actually 2 gates paralleled) which requires both inputs to be high in order to light the LED. You are correct that the LED is on when the inverse signal is high (dry soil), because both inputs have the same signal (the lower input through the pot). As the soil becomes conductive (wetter) the lower input's voltage becomes lower due to the voltage-divider of the pot and the soil. Even though this voltage is lower, it is still above the threshold and therefore is a valid high signal. So the LED remains at full brighness until the voltage-divider reduces the lower input's voltage to its threshold. No dimming. When the lower input's voltage is slightly below or very much below its threshold, then it is a valid low signal and the LED is completely off. If a capacitor to ground is added to the lower input, then its signal will be delayed (until the capacitor charges up to the threshold). If the capacitor is chosen so that it charges quickly with dry soil, then it will charge slower when the voltage divider has a lower voltage. This will create PWM of the LED. Therefore the LED will dim.

JLB, The author of the project replied saying that an additional capacitor is not required, and that he has had several correspondents state that they are satisfied. He also recommends using only Motorola ICs in order to correct a "failure to perform at 3V" problem. I don't believe that the LED can dim without using Pulse-Width-Modulation which requires the time delay created by an additional capacitor in combination with the soil's resistance. Relying on a single manufacturer's part to correct a problem that is caused by a poor choice of logic family (regular CMOS, not guaranteed to work using less than a 3V supply) is bad design. I will analyse PWM to dim the light, and the use of a 74HC00 IC which is guaranteed to work down to a 2V supply, and will allow more output current resulting in a brighter LED. Have you tried adding a capacitor to ground at the right-side probe yet?

MP, Thank-you for correcting your original statements. Are you using translation software? Where are your other corrections that I made? I see your point that a relay coil terminal that has a continuous voltage on it could conduct through a path of dirt to ground and latch-on, and that your suggestion of grounding the coil stops this from occuring. But then the dirt or the PNP will blow-up instead. Kasamiko, How are your relay tests?

MP, 1) Your terms "sink" and "source" are reversed. Sink is used when a device pulls-down a load to ground. Source is used when a device pulls-up a load to B+. 2) How can the PNP have less effect on the supply voltage than an NPN, when their current amounts are the same? 3) How can relay contacts arc, because of a low voltage at the coil? 4) Does the measly 12V attract dirt to the relay like the thousands of volts do at my TV's screen? Doesn't the high mains voltage at the relay contacts attract more dirt than the 12V? 5) Your PNP driver needs an inverter stage, so use an NPN instead.

Electrodoc, Transistor amplifier and simple filter? Geez, I have been using opamps and state-variable filters for 30 years! Russ is right, the voltage gain of T1 is roughly RV1/R6, reduced by negative feedback through R2. But its gain is also reduced by the low input resistance of the T2 stage, which is in parallel with RV1. That is a poor design where its gain goes up when you turn the volume down. It also causes a simple capacitor filter across RV1 to not work properly. If all resistor values of the T1 stage were lower and most resistor values of T2 were higher, then the volume control and simple filter would work much better. But then the lower input resistance of the T1 stage would load-down the microphone (reducing its output), and and the higher output resistance of the T2 stage would be loaded-down by the low input resistance of the T3 stage (reducing the voltage gain of the T2 stage). So what are we going to do? Add another couple of stages? Not yet. Now we are simply going to turn-down the volume control so that the low input resistance of the T2 stage does not load-down RV1 as much. Design of the T1 stage: 1) Choose an input resistance of the T1 stage to be about 5 times the output resistance of the microphone. The microphone has the drain of a FET as its output, which has a very high resistance, so the output resistance of the microphone is just R1. 2) Choose the output resistance of T1 to be 1/5 the input resistance of the following stage. T1's output is its collector, which has a very high resistance, so the output resistance of the T1 stage is simply RV1. 3) For battery operation, choose the current-drain of the T1 stage to be low, therefore the value of RV1 must be high. 4) T1 is a preamp, so its voltage gain must be high. So the value of R6 must be low. Since this circuit doesn't have enough stages, then compromises must be made: 1) The input resistance of the T1 stage cannot be high enough since its gain must be high, but the value of R6 must be low. Its input resistance is almost Beta of T1 (about 200) times R6. As a compromise we can allow the input resistance of the T1 stage to be equal to R1, which is 10K. R1 cannot be decreased since that would reduce the microphone's output level. With a chosen input resistance of the T1 stage of 10K, then the value of R6 is calculated to be about 50 ohms. Use 47 ohms. 2) RV1 must have a high value so that the voltage gain of the T1 stage is high, and that its drain-current is low. Choose a value of 220K for RV1. (to be continued)

Kasamiko, 22K is too high a value for the base resistor of a 9013 transistor that must saturate when driving a 67mA load. The guaranteed current gain of a 9013 is only 64 @ 67mA. Usha marks a gain-bin code on their 2SC9013 transistors. They even claim that their transistors are used in radios that you can drink, and you won't get sick! (See their funny typo error) Their 2SC9013 data sheet is here: http://www.ushasemi.com/pdf/Transistors/2SC9013.pdf Although they show it saturating very well with Ic/Ib = 10, if your 9013 has a gain of 64 then 1mA should be OK . Use 10K for the base resistor. Is the supply 12.7V with the relay activated?

Kasamiko, The BUZ10 and BUZ11 are rated for only 50V, and 75W. The 30A BUZ11 is good for a very simple inverter. 300W would be easy from a single pair, directly driven from a 4047. Newer MOSFETs having a higher current rating (with better thermal conductivity) would operate cooler and allow more output. Hotwaterwizard, If you simply replace your resistor and zener with a pot to make the output voltage adjustable, then the transistor's base current will fry the pot. But maybe a darlington transistor will work.

Electrodoc, I just realised that your kit is designed for voices, not music. C1, C2 and C3 are much too small to pass bass frequencies. Use 0.47 microfarads for C1 and C2, and 1 microfarad for C3. If using polarized capacitors, connect the negative terminal to the transistor's base. Then maybe my previous 200Hz filter will be OK.

Electrodoc, Did my latest modification (100Hz cutoff) and recommendations work? Is the music played through big speakers, or is it live? Please describe the "beat" sound: Bass drum, bongo, wood-blocks or cymbals? Don't connect the capacitor to the wiper.

Hotwaterwizard, That's a great way to modify the 555's internal divider in order to double its time duration to up to 5 minutes. Kasamiko, The 555 doesn't do a very good job at directly driving relays. Its voltage ouyput, with a 15V supply and a 100mA load, is guaranteed to be only 12.75V, which is a 2.25V drop. This drop is more at lower supply voltages. The LM555 data sheet is here: http://www.national.com/ds/LM/LM555.pdf So it may give only 9.5V into your 12V relay, causing intermittent inactivation. Therefore your transistor relay driver is needed. What is the value of the transistor's base resistor?

Badai, Before you said that the appliances are switched-off and NOT unplugged from the mains. Now your objective says that they are switched-off-but-unplugged. Are they plugged or not? I think that your lecturer is crazy to believe that appliances can produce EMI when switched-off, regardless about whether they are plugged-in. Good-luck, again.

Kevin, An emitter follower has a voltage gain of 0.99 or more. It does not have a transition and its output goes from low to high just as fast as its input because its output follows its input. Any very high-speed circuit doesn't have much gain, and any very high-gain circuit doesn't have much speed.