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MP
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I can help with links for the assembly language.
http://www.programmersheaven.com/zone5/cat709/15567.htm
http://www.bipom.com/xasm.htm
http://www.eunet.bg/simtel.net/msdos/asmutl-pre.html
...and perhaps a disassembler?
http://freespace.virgin.net/roger.spriggs/digital.htm
MP -
what are you talking about with 2 of the op amps running open loop? I am looking at this circuit to see what problems you have noted.
MP -
Here is one:
http://www.learn-c.com/schemat.htm
MP -
CDAK, thanks for coming back with a scope diagram. It is not really all that bad. A scope will make things look ugly when they are not perfect. Does your circuit have a little better looking signal when not amplified as much?
You might be able to clean this up a bit with an expandor circuit and then trim down the overall gain. An Expandor circuit will amplify the louder parts and quiet down the softer signals. Then you would not have as much problem with the other sounds.
One such chip is the NE570D compander. This compander chip has two sections which can be wired as an expandor or a compressor. The word compandor or companding a signal refers to using a compressor at the input of a device and then an expandor at the output of the device to return the level to normal. In the process the noise is reduced. I do not think you would need to do all of this. Perhaps only the Expandor part would be needed. I have used this a lot in music equipment that I have designed to get rid of inherent noise. More importantly, background noise. This is not a noise gate. This is completely different. A noise gate will turn your sound down until it reaches a preset threshold. An Expandor increases the dynamic range. It gives you more db distance between the background noise and the applied signal.
Here is a data sheet: http://www.semiconductors.philips.com/acrobat/datasheets/NE570_3.pdf
Hope the info is helpful. It might keep you from having to redesign.
I think there is an application diagram in the data sheet. If it is not clear and you want to go this route, let me know and I will post a diagram.
audioguru: How are all of these changes "sticking to the circuit?" ::)
Also, have you built the circuit with the changes you mentioned or is this in the theory stage? I think this is important to know.
MP -
From your description, it sounds as if you do not have enough current to your H bridge circuit. Check out this link for more on H bridge circuits. However, you might be able to just increase the current available to your present circuit and make it work.
http://home.cogeco.ca/~rpaisley4/HBridge.html
MP -
Hey, I just came across this schematic. Reminded me of yours. The author's name is Bill Bowden. I will give him credit here. His article reads:
The LED traffic Light circuit controls 6 LEDs (red, yellow and green) or both north/south directions and east/west directions. The timing sequence is generated using a CMOS 4017 decade counter and a 555 timer. Counter outputs 1 through 4 are wire ORed using 4 diodes so that the (Red - North/South) and (Green - East/West) LEDs will be on during the first four counts. The fifth count (pin 10) illuminates (Yellow - East/West) and (Red - North/South). Counts 6 through 9 are also wire ORed using diodes to control (Red - East/West) and (Green - North/South). Count 10 (pin 11) controls (Red - East/West) and (Yellow - North/South). The time period for the red and green lamps will be 4 times longer than for the yellow and the complete cycle time can be adjusted with the 47K resistor. The eight 1N914 diodes could be substituted with a dual 4 input OR gate (CD4072).
I thought you might be interested in comparing the two circuits.
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Now where in my post did you read me to mean the diode was in series?
Yes, if you have a fan with this protection, it is parallel, but no it will not blow anything up. Your power supply can handle this. The diode protection and current limiting in the power supply will pull the current down to nothing.
If you buy a replacement cooling fan for your PC from radio shack, they are not going to expect you to know to wire in a diode.
MP -
If I understand the circuit correctly, the 555 is starting the count and the 4017 is counting so that the different lights come on in a sequence. Therefore I would trigger the 555 for a restart or to stop the circuit.
Have you thought about using a microprocessor to control this circuit? You would have a lot more control and could eliminate the 555, transistors and the 4017. You can program micros with basic. Instead of loops of time with counter chips, you would just tell the micro to pause for x number of seconds and watch certain pins for a trigger that can stop the program or start another routine.
MP -
Perhaps this will give you a start:
http://www.funsms.net/sms_tutorial.htm
MP -
Some computer fans do have the diode built into them. If you can reverse the direction of the motor by switching the wires, then it does not. If you can switch the polarity of the wires and it will not run, then there is a diode built into the fan.
MP -
You must send the AT command to pick up the line before the phone will dial out. Otherwise the DTMF tones are not going anywhere. Could this be the problem?
MP -
Here are some links that might get you started.
http://www.myplace.nu/avr/thermo/
http://electronickits.com/kit/complete/meas/ck108sc.pdf
http://www.discovercircuits.com/T/temp-cont.htm
MP -
I think you are on the right track about the light sensing sensors. When the object breaks the beam it can trigger a circuit. If you use two such circuits, and connect them together such as an AND gate, you will eliminate false triggering because both would have to be activated in order to start the trigger action. The best way to achieve this might be to use a laser and LDR (Light Dependent Resistor). One half of the circuit will send the laser light beam and the other half of the circuit (LDR) will receive it. There might be such a circuit in the projects section of this site. If not, I will look around. I know I have seen an already made design for a laser trigger circuit somewhere.
MP -
There are a lot of methods for temperature control. Surely you have something in mind already. How did you want to go about this? Let us know something about the hatchery and the temperatures you need. I assume it is only for heat and there is no need for cooling? What is the source of the heat? How is it switched on and off? What voltage will you be switching on and off?
MP -
The regulator is not changing the voltage at this end. It is already regulated. Larger caps on the output of the regulator will help curb fluctuations in voltage caused by the circuit that is being powered much better than small ones. In many circuits, I see both a small and a large cap in parallel. This is because of inherent noise that might be generated by the circuit being powered.
A fluctuating DC voltage is in a sense an AC voltage. Remember, DC does not pass through the capacitor. It is only the AC signal that will go through it. The size of the capacitor is determined with a formula for frequency.
MP -
You will have the same EMF effect when the motors for the fan come on like what you have when the coil of the relay is energized. It is a good plan for all motor type circuits. You would not see a difference in the way your circuit operates. It is for protection, like adding a fuse.
MP -
It is probably more dependent upon who IBM purchased them from. I do not think they make their own.
How many wires do you have and what are their colors? This will be more helpful. Also, I usually measure the resistance from wire to wire to map out the windings. You will find the coil resistance this way and find out which wires are connected to which internl coils in this manner. If the stepper was in IBM equipment, it is probably a 5VDC stepper. I could be wrong on this, but I have never seen IBM use a different voltage for steppers in their equipment (unless it is very old). Also, this is a safe voltage to try. If you know this and the coils resistance, you no longer need a data sheet, because you can tell how to step it from this information.
Here is a link to a site that has information regarding IBM steppers pulled from old equipment. Your pin-out might be here:
http://www.doc.ic.ac.uk/~ih/doc/stepper/
Please let us know how you made out.
MP -
I was thinking about this in an audio type of set up. Car stereos need a large bypass capacitor on the 12 VDC power side to help deliver the good base response from the newer high power amplifiers. Usually a 1 farad capacitor is used. However, such large value capacitors are very expensive. If one could be made easy enough with aluminum foil plates and paper insulators but not require a trailer to carry it ;D, this would be a great alternative.
I can certainly see where a fuse would be necessary on this in case of a short in the home made device. Car batteries have a lot of current capability.
MP -
audioguru, good eyes! Yes. The relays will not work if they are 12 VDC coils and only have 5 VDC to activate them
MP -
Tone control takes a very stable circuit. A circuit which just barely passes would not be workable in the audio field. It certainly would not allow you the ability to change a resistor or capacitor value and cover a wider range of frequencies.
Output bias is not needed.
You need more study of the op-amp before drawing such conclusions about how workable a design is. To answer your queries, look over the data sheet for the LM741. This is a pretty common op-amp. BTW, not low current transistors, high input impedance.
MP -
Yes, just like the example in my last post. That is what the diode is there for. This is also a relay driver. By the way, how much current does the relay require to turn on the coil? Do I recall that the switch is not really a switch? That it is another device? You should check to be sure you have enough current from this device to power the relay coils.
MP -
I saw your posted schematic but did not understand what you were trying to accomplish, so had hoped someone more familiar with your hobby would converse with you. ( I am not an HO enthusiast.)
I do not see a way to trip the circuit. It is only connected to a 555 timer and thus will always run. Am I missing something? What starts this procedure to turn on the lights? I know that it is voltage applied to the circuit, but when is voltage applied to the circuit? And how could it be falsely tripped?
If you have been working on this for 3 months, don't give up if you do not get a reply in 3 days. You are not wasting anyone's time.
MP -
How is the A/D reading the input? I mean is it placing the signal on the parallel port, serial port or where? Or did you assign it an IRQ?
I am not sure that even with this information I will be able to help, but I think this information will be needed in order to get you the help you need. The ISA bus has many terminations and it is not clear what you have connect to on this card.
MP -
In other terms, some reason is causing the load to be grounded through the rheostat. This could be the polarity of the plug, a mis-wired terminal or something else. It is not possible to go further without seeing the schematic or wirng diagram. Since you have two and one is working, you can examine the working unit to see what is wired differently on the other one.
MP
Electronic Stethoscope
in Projects Q/A
Posted
audioguru:
I would have built this dofferently myself. However, I would have built it, tested it, and posted it at the time.
I see what you are talking about with the feedback in the schematic. I am not the author of this project and will not speculate what he meant to do. However, it should be noted that there is not always a feedback resistor used on an op amp and these are not open inputs. Sometimes op amps have a different purpose than amplification of voltage. Also, U3 is a buffer. If you get rid of this, the pot right after this will not work as intended. Especially if you replace R9 with wire. If you use a 386 power amp chip, you might as well get rid of all the op amps, because they would not be needed. The 386 can power a head phone without preamplification.
The C2/R2 combination determines the Low frequency cut off. The author has chosen .047uf and 2.2k, which dictates a 1.6KHZ low cut off. If you change the value of this capacitor to 4.7uf as you have suggested, the low frequency cut off will be changed to approximately 16 Hz as you have indicated. This will pass more low frequencies in the circuit, but I am not so sure that the heartbeat pickup is intended to duplicate the Pink Floyd imitation of a heartbeat. Medical equipment usually uses a higher frequency in the middle or lower end of the speech spectrum. Not in the lower end of the full hearing range. The low frequencies also bring in more hum and interference from other devices used in the room.
Lastly, let me say this: When someone finds a circuit that is not correct, I think that it is welcome by all to hear about it. But the changes that are welcomed by all come from someone building a working circuit and posting the fix for the circuit.
MP