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Thanks for your advice on the BJT. I had also thought of that since they have a much larger linear region. The problem is that they are current driven instead of voltage driven like MOSFET. I'm not sure how much current my voltage source can sink, but it bet it's not much. I guess I could...

Thank you very much for all of your inputs. I am beginning to think the problem might be the fact that my load resistance is so low. Here is the rest of my values if it helps to figure out what is going on. Current limit is 6 A for the first 125ms after battery connection. Load resistance is...

A couple additions to the previous posts. Using an op-amp is a good way to amplify your voltages. I just wanted to point out that you can get a dual op-amp IC very cheaply, and it doesn't take up much space on a PCB. That would be preferable to two discrete op amp chips. Secondly, to go from...

Hello. I am designing a circuit to perform a discharge test on a battery. The load profile consists of several discrete resistance values that I will switch in and out of the load path at set times using an analog output controller and some power MOSFETs. The load bank design is almost...

I wish you could just go online and do it. Of course that opens up a whole new set of possible ways that the vote could be corrupted or compromised. But it seems like if they have a way to encrypt your credit card transactions when you order something online, then they ought to be able to...

The same company that makes HFSS (Ansoft) makes another product called Maxwell 3D. It's mainly for modeling magnetic fields but maybe you could use it somehow on your application. Higgler - I'm working with Toyon right now on a set of GPS antennas for the GIF fuze. Nice to meet you. :-)

This is a pretty cool project. If you want to invest an a wireless card where you can hook an external antenna up, then I would try putting a powered RF pre-amp at your frequency in beween an antenna and the card. Remember that you are going to amplify not just the signal but the whole...

Check this out. http://www.motionnet.com/ It's an engineering directory that lists companies over a wide array of motor and other motion catagories.

Checkout "The Complete RF Designer's Handbook". http://www.amazon.com/exec/obidos/ASIN/0790611473/qid=1112362141/sr=2-2/ref=pd_bbs_b_2_2/104-6924305-3121546

There is a company called Toyon that has been designing a small (3in. x 1in.) pair of GPS patch antennas for a defense project. I can tell you that it's not an easy thing to do. They have many more problems to worry about than you would, such as aero-heating, mechanical shock survivability...

If you can use a stepper motor than you might not need any feedback control. You can just move the motor exactly the number of steps it takes to achieve your positions, and assuming that you do not stall or otherwise overload the motor , then your position will be accurate.

If the user is going to already be using a computer then you could just hook a mic up to the soundcard. There are many programs out there that will let you record. Windows even has one built in. If not, then there are about a million voice recording devices out there for making personal...

What kind of DC motor is it? If it's a brushed DC motor then you wouldn't really even need a driver (more voltage makes it go faster) so that could save you some money there. However, if you are using a brushless motor then you would need a driver since they are driven with a PWM power...

Go and check out the National Instrument Developer Zone. They have lots of information there. http://zone.ni.com/

I am assuming that you just haved a design, not an actual proto-type of the circuit correct? If you had a real one, then you could just hook it up to a network analyzer and get the loss between your two ports.

Cool glad that you figured it out. Just to clarify, you should have no problem running the gate of a FET directly from the PIC. In fact, I am doing that right now with a circuit that I designed. The PIC pins can usually sink between 10 and 25mA depending on which model you get. I am passing...

Check out Staco for some nice Variacs. They even have digital ones now. www.variac.com

Do you have access to a program like LabVIEW, HP VEE, or MatLab? Those programs would be great to take in data and display it in all kinds of formats.

I use ExpressPCB a lot. They give you a free program that has schematic capture and PCB layout, and then you send the design to them electronically and you get your boards back in a few days. It's pretty economical for low count orders too, so it would be perfect for a school.

Check out Ansoft. They have a couple of packages that you could use to model antennas. One is called HFSS, and the other is called Maxwell.