login
MP
-
Posts
3,399 -
Joined
-
Last visited
Never
Content Type
Profiles
Forums
Events
Posts posted by MP
-
-
-
audioguru, the term "floating input" refers to nothing connected. Any 741 or similar type op-amp will have an input impedance of approximately 2 MegOhms on an input when the other input pin is connected to ground. This would tell most that the input is not floating. You also have a resistance value to work with. You have a strange impression of "how an op-amp is intended" to be used. There is no specified intended use. There are a wide variety of uses. The formula for gain of an op-amp does not factor in a resistor with a bias voltage. If it were a necessary part of the circuit, the data sheet would indicate this.
i have attached some examples of circuits without the bias you claim is a must:
-
audioguru, CDAK made the project work without making this list of changes. I hope that we can hear from him soon.
MP -
Good link for Eagle Tutorial. I will also add two. Anyone got any others? It is nice to have as many sources as possible.
http://www.interq.or.jp/japan/se-inoue/e_eagle.htm
http://www.precma.com/informatica/tutorial.htm
MP -
Op amps have an input impedance of approximately 2 Meg ohms to ground. The input of an op-amp is not floating. This is an application where you want a high input impedance. I have not tried this circuit and I cannot tell you if it functions as is without a little bench work. But if you are condemning the circuit for this reason, it is the wrong reason. Also note the function of this circuit. It is not a linear type of circuit.
MP -
Actually, Deep Cycle batteries have their own inherent problems. I would stick with the common less expensive automotive battery if you must use a lead acid battery. LDanielRosa is correct that the automotive battery does not take well to discharge. You should make sure that the battery is kept charged. Another thing that most design engineers leave out of a design is some sort of loading. Batteries also do not like to be left dormant. If you will use a battery in a system where it will not be in use for long periods of time, you should add some type of loading circuit that comes on at a specific time interval to keep the battery in some type of light function instead of just sitting there dormant. Another concern is battery temperature. If the battery will not be indoors, then the temperature should be monitored. Most people know that batteries do not like to get real warm which is a reaction usually due to charging, but batteries do not like the cold temperatures either. In places where the battery will be stored in cold temperatures and not used a lot, I usually allow a heater circuit as the loading circuit that I just mentioned. This will keep the battery active and will keep the temperature at a level which will allow the battery to last longer.
All of the little tricks for batteries help to keep them functioning longer so that you do not need to replace them quite as often.
MP -
shiva, another group member with user name CDAK also made this unit and also had some problems with it. He has made some modifications. I am awaiting the final changes. If you will look through this thread, he describes the changes he has made.
MP -
Hotwaterwizard,
Our project's receiver has an opamp without an input bias voltage. The receiver will probably be a lot more sensitive if pin3 is biased to half-supply with a couple of 2.2M resistors.
An op-amp does not require an input bias voltage. I see no problem with the circuit "as is".
MP
-
As audioguru has suggested, you should post the specs for the 12V relays. Also, what are you using for a power source?
Right off, I do not see diodes across the relay coils to protect the chip against spiking when the relay activates. It is also not a good idea to connect a chip directly to the base of a transistor.
MP -
Thanks, ante. I saw the link for the inverter chip. I thought you were discussing an inverter schematic which used this chip in it. My mistake.
MP -
MP,
The engineer did not earth-ground the circuit's 0V output. He was simply showing a common link between the 7824's zener and system 0V buss.
The red line with a ground marker on the bottom of it which is tied to the power supply low side output indicates that this line is grounded. If he was only indicating where the zener connects, he used the wrong symbol.
MP
-
ante, 7924 is a negative voltage regulator. Is this what you mean?
MP -
Nishi,
The other guy that you are agreeing with mis-read the original post. The original post was not about voltage ratio. It was about current. There are formulas for this. Winding resistance has everything to do with current. If you have an unknown transformer, you are going to run a voltage through it to find out what it will do? How much voltage? You have to make a guess. I have a poor opinion about bench tests that start with guessing and work their way from there.
This site is filled with beginners looking for answers. They do not have high tech equipment. So, when a guy says just connect it to the mains and see what it does, that worries me a bit.
MP -
would someone like to post a link or schematic of theTTL inverter you are talking about so that the rest of us can follow?
Thanks.
MP -
...and I would love if anyone would point out any mistake that the engineer has taken ... I doubt it thou ! :D he's the company pedaments lol
I did not mean to sound critical. I was responding to your above request. It is my opinion that the higher transformer will not work with this circuit because of the current limiting devices used. One example: Q3 and U3 have a critical role in the current limiting circuit (why I pointed you to the description of how it works), but your company engineer has isolated them from the raw power source and has regulated this buss. He has also caused this circuit to have the negative side grounded, which limits the uses of the power supply. It cannot be used as a floating supply or in conjunction with another supply in certain configurations. I have not looked closely, but I am sure there are other considerations, too.
There are many designs for power supplies. I am wondering why not choose one which has the capability you need instead of trying to tweak on a design that is not intended for your specific use. Perhaps I walked into the conversation a little late, and for that I apologize.
MP
-
Or else use a very high speed driller (30,000 RPM) like mine and it will drill the PCB instantly without running off before cutting. Drawbeck is that you must aim right or else it will drill were you do not want it
My drill is also 30,000 RPM and I have noticed that if the bits are new then it is how you have described. But if you plan on using them a number of times, you will get the walking problem. Even on my CNC I see this problem. Only the walking causes the bit to break. Besides, you are dulling your bits faster by drilling through a copper pad. A simple scratch of the etch resist will allow the etchant to make your center hole. Why waste bits?
MP
-
xenobius,
You should compare these changes with the paragraph in the project of how the supply works. It looks like there will be problems with the limiting circuit with these changes.
MP -
This is why it is better to use a layout that shows the hole in the pad. There will be a little hole in the copper which makes drilling easier. On solid pads, the drill bits tend to walk before biting in.
MP -
Why not make your own circuit board with either perf board or using one of the kits with etchant? If you are in a great hurry, perf board would be a good way to go. You could use wire wrap to make your connections.
MP -
I do not know of any alignment tricks other than using a magnifier so that the pads are easier to see when you drill them.
However, when you make a mistake like this, you can still use the hole. Just bend the leg a little and make sure you are not touching another pad. You might have to remove a little copper to insure there is not a connection where you do not want it.
MP -
Hey guys!
When I say USING it, I mean it!
My 486 is used every day on the internet (cable) for surfing, e-mail, ordering parts and for word-processing invoices, etc. It is reliably running Windows 98, 1st Edition ......
.....Any other challengers?
I would not exactly call this reliable, noting the above comments... You have also wasted mixos time for a problem that does not exist on this system.
It seems you have two choices:
Upgrade or stop complaining.
MP
-
The digital pots work fine in real world electronics.
Audioguru, you have quite a habit of starting a new topic within the thread of a different topic. This thread is about LM3886. To go further on digital pots, you need to start a new topic. Otherwise I will have to chop up the posts again.
MP -
PAIA electronics used to sell kits for synthesizers. You might be able to find some of their stuff on the web. They went out of business some time ago when they started gearing their synthesizers to commadore PET control. I do not think it was a good combination.
Every so often, I see some of their VCOs and filter circuits on the web.
MP -
[snip] ...only OPERATING appliances emit EMI... [snip]
Many of the newer appliances have things running even when the appliance is not in use. Most easily recognized is the clock, but some have other devices running caused by microprocessor circuits. In the case of these appliances, even unplugging them would allow the system to run on the back up memory for a small period. Perhaps this is where this "crazy" lecturer is going?
Although this makes no difference in most cases, if one is setting up a solar system for a house, these little draws on the system really add up from appliance to appliance. (Another point of interest)
I think we are sometimes quick to call someone crazy when we do not understand why they do what they do.
MP
was Re:Ir-remote Now is: Op Amp discussion
in Electronic Projects Design/Ideas
Posted
The last post was part of the fron end of a well known Fender Bass amp. The one before that is a well known guitat effect. Here I have added another well tested and favored guitar effect.
Although you will see different configurations, you will note from the examples that all op amp uses do not need a bias voltage.
MP