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MP
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Posts posted by MP
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Joe,
Here is a circuit for a 0 to 60 second stop watch. This should work for your purpose. It has "hold" and "reset".
MP
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One thing to keep in mind if you are adding the opto coupler in series with the existing LED is that the opto coupler has a LED in it which is going to drop your voltage and change the available current to both devices. When calculating current in a circuit with an LED, you always subtract the LED voltage drop from the circuit before dividing into the value of the resistor, thus, in this design, you might have to remove the resistor in the original circuit and replace it with a different value. Not a big change, but something to be aware of in case the original limiting resistor will only feed the existing LED.
MP -
It is not a good board layout practice to use a board layer for this purpose.
MP -
Gogo,
Good find! The older versions did not have a manual.
For those browsing the Eaglesoft website, it is on the page with the program downloads. You have to keep scrolling down to find it.
Here it is. I noticed there is now a tutorial on the same page.
Note: I have also moved this topic from Projects Q/A to this forum since it is about CAD.
MP -
For best results, you would treat all three as 3 separate circuits and then tie them all together at a single point at the chassis. Otherwise, you could have interference between you analog and digital circuitry.
MP -
There would be many ways to do this. Some require tearing into the circuit and making some measurements and some do not.
Do you still need to see the LED? If not, you could install a LDR on it and use the LDR as part of a voltage divider to turn on a relay. This would probably be the easiest method.
Another way is to tear into the device and measure how much voltage and current you have available. Then you can calculate a bipolar transistor to be used as a switch. You might also want to look farther ahead on the circuit and see what is turning on the LED. You might already have what you need to control a relay ahead of the drop-down resistor that limits the current to the LED.
Hope some of this starts you with some ideas. Any chance you have a schematic? It would be very helpful and would make the project a lot easier.
MP -
I don't think Eagle has a manual. Here are links to some tutorials:
http://www.interq.or.jp/japan/se-inoue/e_eagle.htm
http://www.precma.com/informatica/tutorial.htm
MP -
Think of the windings as resistors. With power turned off, you measured two sets with the same ohm readings, right? These most likely each have a red and a black wire. Mark them as secondary red A and secondary Black A for the one set and secondary red B and secondary black B for the other set. These are your two 120V sections. Hope that makes it a little clearer.
MP -
Cavalier,
Since you have AC voltage, why not use capacitors and diodes to make a voltage double. Then you can rectify and regulate the voltage from there.
The drawback, of course, is that you lose current with a voltage doubler. However, this might not be a problem since the voltage is coming from a generator.
MP -
Is there an easy way to identify what two wires these should be?
David, with no electric connected to the transformer, use an ohmmeter to determine which wires are going to the two individual secondary windings. You have two windings, which you hope are the same. You should have two combinations that give you the same or very close to the same ohm reading, where other combinations are infinite or some very high number, depending upon ohmmeter and how it is configured. It is possible to have a transformer that can give you two different ohm readings, which relates to two different voltages from the two secondary windings. If this is the case, this transformer will not work for your purpose.
MP
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The problem is after i finished and tested. The result not very accurate.. Y??? I buy the correct reading caps. How can it give me unacceptable reading. Ex, 63PF from my mini pro, i install it to the machine, it's give a reading of 70PF.. Wow.. That out of range.. How come?? I need ur HELP guys.. Really thankfully if you guys help me solved the problem..
What is the tolerance spec on your capacitors? If you use a cap with 10% tolerance, it would be normal to see 70 pf from a 63 pf cap. If you use a 20% tolerance cap you could see worse.
You need to find 1% tolerance capacitors to make this work properly. Then follow good grounding guidelines. Depending upon the specifications of the instrument you are connecting to the input, you could still need a buffer or a drive circuit to help with any signal loss. What tolerance does the input instrument allow for ? In other words, how much error can you allow? There will always be some error. You have to allow for this margin. You also have to use a metal enclosure which has the same grounding potential as the shield on your cables. Even with this, since you are working with capacitance, you can see differences with the box open as opposed to what you see when the box is closed. Depending upon the test equipment used, you could even see different capacitance when the test probe is connected and when it is not.
MP
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What are you looking for? The pdf file was a pretty good sized schematic with multiple axis. If you still need more schematics, list some specifics and we can go from there.
MP -
Looks like you forgot to 1/x your sum. I am assuming you used the parallel formula and came up with 1/50+1/50+1/50....etc and came up with a sum of 0.2. Answer is actually 1/x, thus 1/0.2 = 5. Correct answer is 5.
MP -
Joe,
If you have some experience with microcontrollers, you can do this pretty easily. Count the pulses coming in and send a pulse out another pin after every so many counts. As long as you use a micro with a faster clock than 4 Mhz, it will work fine. This is on the same lines as what hotwaterwizard, ughadoo and audioguru suggested but with less parts count.
MP -
Here is another...
MP
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You would use different components. I have attached one example. There are many ways to control steppers.
MP -
According to the author's site for the software LCD Smartie, he has added 4X20 support to this program in his latest version. Connections to the LCD are always the same, so it looks like it is a matter of downloading the latest software. Follow the links from the project to the author's site and browse for the latest version of his program to see what features are included.
MP -
Your traces are plenty big enough for this.
MP -
Hi Nef,
I think there was some confusion from the discussion about the different designs on our site and on the author's site. I would recommend building the project as it is on this site and then making any adjustments as needed to get the colors and brightness where you want it. The 10K resistors on the project will not allow the micro or transistors to burn up. The project is using PWM instead of a straight DC signal, so there is much latitude before parts failure
MP -
how exactly could I add a timer or some sort of other thing
One method is to use a transistor as a switch that has the base controlled by a 555 timer used as a monostable. You would calculate the monostable for the amount of time needed. If you are not experienced in this, there are actually 555 timer calculators on the web that will help you. It is also a good way to learn about the calculations with a 555.
MP -
Hi Korslain,
Welcome to Electronics-Lab!
There are quite a few factors involved in this. Here is a portion of an ohm's law tutorial that goes a little into depth about body resistance:
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
Hope this helps. Also note that there are books written about this very subject. Much research has been done in this area.
MP -
The window switching is handled inside the door. Just find the power feed from the switch. You can feed this on a timer since the door circuit will sense a load and nothing will happen if the voltage or switch is activated too long. Note that you will need to tear into all the doors to build this circuit. Once inside, you have the option of building on/off circuits connected to one source or an RF transmitter. RF transmission would be easier in the sense that you would not have to run wiring to all of the doors. Be careful with an RF transmitter, though. You could be driving down the road and some kind of radio noise could cause all of your windows to go down. You will certainly want to incorporate some kind of code circuit and not just an on/off RF signal.
Hope that gives you a few ideas to start.
MP -
Are you sure the teacher didn't say "timing diagram" and not "truth table"? 4017 is a decade counter.
MP -
Hi Alex,
Firstly, Welcome to the forum!
Do you have experience programming a micro? This would be the most interesting way to do it. Otherwise, you might want to use a timer. Either way, you really do not need a water monitor, per se. You just need a circuit that will activate a relay at a predetermined moisture level or predetermined time interval.
For either application, since the moisture in the soil changes the resistance of the soil, you can use a circuit which uses the resistance of the soil in a voltage divider to activate a comparator or transistor, then to a relay that activates the watering mechanism. For the timer idea, you would want to build a clock circuit and activate the relay at predetermined time periods.
Hopefully, this gives you some ideas. Good luck with the project!
MP
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I am not familiar with your program, but you should look for 4511, 4518 and 4060 chips. Forget the MC1. You won't see that in your list. Does that help?
MP