MP

I have tried out their software and I have gotten pricing from them using the board layout program. The two quotes I got were not too bad, but were in the ball park with some other companies on the web. The big concern to me is this: I make all of my designs in their software and I am going about my business as a happy customer and BOOM! The day arrives where their prices suck. Now all of my boards are done in their layout program so what do I do? I bite the bullet and pay them more than what I want, or I redesign all of my circuit boards so that they are in a format that anyone can use. Alternative? Yes, use a different free layout software (and there are many) which will allow you to output the artwork in Gerber format. This is the accepted standard for any board house. Yes, even PCBExpress will take them. This way you will never get caught in a situation such as the above. MP

Kevin, when I mentioned that you might want to send a personal message to the author of the article, I was referring to the "instant message" feature. Click on his name in one of his posts and you will be able to send him a personal message from this site. MP

Bob, building from the schematic that Mike has provided would probably be the cheapest way to get this supply. You can purchase from surplus parts outlets. One such outlet is All Electronics. The highest cost will be the transformer. And here is an alternative: If you do not want to make your own power supply, you might look at their wall transformers. 2 of these will give you what you need. You will want to switch the polarity of one of them to get the negative output. In other words, the tip of one and the outer barrel of the output wire on the other will be connected to ground. The other two connections will then give you + and - voltage out. Here is a link to their wall 15 volt transformers. If you are not used to working with mains voltage, then this might be a solution for you. http://www.allelectronics.com/cgi-bin/category.cgi?category=790&item=ACTX-152&type=store MP

Shmitt, here is the basic template for a state variable filter with gain. The 4th op-amp determines gain. All of the calculations are on the schematic. All you have to do is plug in your frequency and a few other values and you have a state variable filter. MP

Yeah, but you can only use the free layout program to have "them" make your boards. Takes the bubble out of free, wouldn't you say? MP

JamesTh777: Just a comment here about your tag line. I think that if all of the Christians could agree not to plug Christ and all the Muslims would agree to not plug Allah, as well as the Krishnas, Buddhists, etc. also holding back their views on life, then we could also expect the Satan worshippers to not plug satan on this site. Why open the door for religious wars on a site where everyone in the world is coming to share their experience in electronics? We all have different views on life. One thing we have in common here is electronics. I for one, really do not want to come here to see advertisements of any kind. Thanks for understanding. MP

Here, try this. The Dallas digital pots are not that hard to figure. This is an application note from Dallas showing how. MP Dalls_Digital_Pots-app69.pdf

Designing your own filters requires a bit of calculation. You need to know what you expect for damping factor, Q, bandwidth, and gain as well as the center frequency. The standard State variable filter design uses 3 op-amps, which I think will give you an inverted output. If your design gives you an inverted output, all you have to do is add an op-amp buffer stage to change it. How much time do you have to learn this? You said you are trying to design one. What do you have so far? MP

You would not refer to a regulator as a junction of two signals since the voltage at both sides of the regulator are from the same source. A junction would also imply the source comes from different directions, and the regulator is working with DC, which means direction of both sides of the regulator are the same. The output voltage of the regulator is the input voltage with a change made to it. I hope this explanation is helpful. MP

For some time I was making sure that I had the 4 corner pins for anchors and I left the other unneeded pads off my drawing as they were not needed. However, later I found that this was confusing to others as to which IC was there and left me the problem of making special parts drawings in the cad programs I used later on. Finally, I just left the package as is, drilled the holes and simply did not route the pads to anything as Billy has mentioned. Sometimes we make more work for ourselves in trying to eliminate some work. MP

I think that I should add: I am very grateful to these companies for providing samples for my prototyping purposes. We might rate them as fast or slow or grumble about package types available, but the bottom line is, they are free and an expense I do not have to provide to find out something is not what I want. I did not want my previous post(s) to seem like I was not appreciative of this service from them. MP

You might find it better to use this one for the specs you have described. http://www.electronics-lab.com/projects/power/027/index.html and start a new thread on modifications to this one, although from your description, it sounds like it might be ok as is. MP

Bascom AVR compiler has the dtmf output built in and also the A to D in your other post. The compiler is free to code up to 2K of the memory. You can download it from www.mcselec.com MP

gaark, if you can attach a schematic or a link to the circuit you are working on, it would be helpful to others to see what you already have in the circuit. I have noticed that the posts which get the most replies on this forum are those with an example attached. It makes commenting easier. MP

Hi Jandro, I have never seen anyone use this application. Perhaps the simplest way to do it would be to have the current change the intensity of light which activates a light sensitive resistor where the light sensitive resistor takes the place of the pot. You could make your own custom package if needed. I am sure there are many other ways to do it as well. MP

http://content.honeywell.com/sensing/prodinfo/humiditymoisture/ MP

Yes, I know this. But the ones I have been requesting lately are not available in this package as samples. It looks as if I am going to spend a little time making adapter boards. ::) MP

That is the nice thing about National Semiconductor. They usually print an application note somewhere. See Application Note # 256. http://www.nalanda.nitc.ac.in/industry/appnotes/Natsemi/AN-256.pdf MP

I have noticed lately that all my free samples from Maxim have been very small surface mount rather than pdip. Anyone else getting this? Sure makes for hard prototyping. MP

As Mixos has said, you would only use earth ground or case ground when the circuit requires it. Some circuits depend upon a floating voltage and will not work when the common of the circuit is tied to earth ground. If you would like to post a particular circuit or link, everyone could comment further. MP

Siddu, this is very interesting. Do you know of a website with more information regarding this? Any schematic examples of designs used to do this? MP

Yes, and please do not forget the one right here on this website.... Uses a 555 timer IC. http://www.electronics-lab.com/projects/test/006/index.html ;) MP

Here is an update: VPC has it. From their description: ***3M discontinued Dynamark.*** Quick-Mark Quick-Mark has replaced 3M's Dynamark as the preferred method for short run, rapid, in-house production of durable, self-adhesive signs, placards. Quick-Mark is UL approved and is used by NASA on the space station and shuttle. http://www.vpcinc.com/Products/dynamark.htm The down side of this is that they have increased the price from what I paid for it several years ago with 3M. Perhaps it is worth more, now that they use it in the space station and space shuttle. ::) MP

Doom.com charges $50 per month for membership before they will allow you the information... :o Anyone have an account there? MP

I do not think this is what they were referring to. I think it is a question about the LMXX schematic. However, I have not seen very many tansformers with a secondary of 7 volts that have much current rating. If current is a consideration, then perhaps we should know the current needed of this circuit. If you need to limit yourself to no more than 5 volts such as used with microprocessors, then use the zener/resistor/caps schematic as is. If you need at least 5 volts, then yes, a 5.1 volt zener is better to use. Bogdan, why don't you also post your schematic with a transistor so that there is another choice? MP