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  1. Maybe this is a little late since you seem to have already figured out what you want to know, but maybe I can help you a little bit. This does not apply to airplanes, since airplanes don't go backwards, but many electric radio controlled cars do go backwards. I am unsure if this applies to ones with brushless motors, but I don't see why not. In RC cars with motors that do go backwards, a pulse of 1ms usually means full speed in reverse. 1.5ms (or 1500 microseconds) means stop, and 2ms means full speed forward. However, in a car without reverse, audioguru was right. 1ms would be stopped or really slow, and 2ms would be full speed. Hope this helped you, at least a little bit. ;D
  2. I'm looking for a little wireless camera. Here's what I need it to have/do: -Color -Digital -2.4 or 5.8 Ghz (not completely necessary, but it would be nice) -USB receiver (sends video to computer via USB port) -Powered by 5V (9V would be fine also, but I would prefer 5V) -Fairly decent quality (basically if its fairly clear it's fine) -Audio not necessary -Small (1.5 x 1.5 inches or less) -Fairly low cost ($100 or less, preferably in the $40-80 range, if possible) The main features I care about are USB compatible, digital, and small. The other stuff is negotiable. If anyone knows of a camera that seems to fit these specs, please post about it and let me know. This is for one of my electronics projects I'm working on right now. I have a tiny camera, but it's not very good. Thanks for the help. ;D
  3. That's what I thought. After I posted, I tried using a return wire and it seemed to work. However, something strange is happening. In my project I'm working on, I basically have a custom made USB device controlling transistors. I tried using the return wire, but it wasn't working correctly. So I removed it. Now it works. I only have positive voltage wires connected from the outputs on my micro in my USB device to the transistors. There is absolutely no return wire. I looked it all over, and I can't find any way I would be completing the circuit. But it works. That's what I'm confused about. I have a battery powered circuit with ten transistors. The ONLY wires connected fromthe microcontoller in the USB circuit (USB circuit is powered by USB port) to the transistor circuit are the ten wires connecting the micro's digital outputs to the bases of the ten transistors in the other circuit. Since one circuit is powered by a battery, there is no way they have the same ground because they are plugged into the same house circuit (they aren't plugged into the same house circuit, I mean). And here's the really wierd part. I can't measure any connectivity between the emitter and collector of any of the transistos even when they seem to be working. But let me clarify something. It's hard to explain my project, but I'll do my best. I took apart the controller for a semi-decent radio-controlled car (it has multiple steering steps and stuff, but it's still not like hobby-class or anything). I wanted to be able to control the car with a joystick on my computer, so I studied it and figured out how it works. I'll still not clear on how it does it, but I figured out the basic idea of how the positions of the controller's (the rc car's controller) steering wheel and throttle trigger are found. For both the steering and throttle, there is a curved group of metal contacts. There are four rows, with multiple small rectangles spaced out over the curve. As the steering wheel or throttle trigger is moved, it slides a metal plate over the contacts, completing a circuit between the ones it is on. The bottow row is one long solid contact that is the common. The rest of the contacts are connected to positive voltages. The metal plate connects them to the common contact, and somehow the controller can figure out which contacts are "connected" to the common contact and calculate the position of the steering wheel or throttle trigger. Since multiple contacts can be "connected" to the common one via the metal plate, I'm not sure how this works since each contact is connected to a positive voltage. What I'm trying to say is I don't know what method the conroller's micro uses to determine what contacts are shorted to the common one. It can't be based on voltage because there would be multiple voltages connected to the common and I don't think that would work. But whatever it does, I figured out that all I needed to do was have a microcontroller control transistors that would do the function of the metal plate by connecting the contacts (actually, I connected the transistors to the wires, not the actualy contacts) to the common one to simulate the different positions of the steering wheel or throttle trigger on the conroller. Right now, it is working great. I wrote a Visual Basic application to communicate with the joystick and with my USB device that controls the transistors. It works great and its kind of fun to mess around with. But anyway, my whole point is that I have no return wire whatsoever, but the transistors are still being triggered or something. I can't measure connectivity with my multimeter across the emitter and collector, but my circuit is working. It's really weird. If I try to use a return wire, it messes things up and causes the steering servo on the car to jitter a lot and I think it's confusing the controller by messing things up somehow. I can't figure out what method the contoller is using to figure out which contacts are shorted to the common, but whatever the method is it would seem that I need the transistors to work right. I can't measure any voltage on the emitters though. Sorry about such a long explanation, but I can't find a way to make this really clear. It's really weird. It's like the transistors aren't working, but they're definately affecting my circuit. Because it works. Really weird... Anyway, thanks for the answer to my original question. :)
  4. I have never been able to get a clear answer on this. Can I use a separate power source to trigger a transistor. By this I mean a positive voltage from a source other than the circuit the transistor is in. The ONLY connection from the separate power source to the circuit with the transistor would be the positive voltage to the base of the transistor. I have tried this and it doesn't seem to work, but I've been told it does. If this doesn't work, what is a way that would allow me to use a positive voltage from a separate power source to trigger a transistor? Thanks. ;D
  5. Ok, I see know. This is beginning to make more sense. I still couldn't figure out what parts to use all by myself, but now I have a better understanding of what the parts are for. Thank you so much for helping me understand more. ;D
  6. Thats ok, I didn't expect you to know everything about it. I just need some help learning, piece by piece. So most (or all) of the capictors are there to lower impedance? That makes a little more sense now. Just a few more questions. What is the purpose of the crystal? I kind of understand what a crystal does, but I don't really understand its use here. Could you explain that a little? Last question. Inductors filter out signals of the wrong frequency, do they not? So is that what they are helping with here, limiting the input signal from the antenna to what is needed?
  7. I guess I was getting things mixed up because I didn't actually look at the schematic while I was explaining, I was just going by memory. But yes, that is the schematic I was talking about. I understand what a 16mhz crystal is and how to identify it, I was just asking how I know what value of crystal to use. I didn't realize it said to use a 16mhz one, so nevermind on that quesion. ;) As for the capacitors and resistors. I understand what each does, but I've never really been able to figure out why they are used where they are. Obviously resistors are used to limit current, so in some situations I understand their use. But when they are used to connect, say, the IREF pin to ground, I have no idea why and it makes things confusing for me. Could you explain the basic idea/reason for why you would use resistors going to ground such as in IREF's case? And could you please explain the basic idea for why you would use a bunch of capacitors going to ground as they are being used, in say the upper left section of the schematic? Capacitors are generally used to keep things smooth and to reduce sudden changes in voltage, aren't they? I am going to buy the assembled modules, but in the future I will want to build my own so I can learn more in electronics, and because it will be more convenient in my projects. I am also having trouble understaning what some of the pins are for because I can't find a good description and I don't know what they mean. Here is a list of the pin functions from the datasheet. I have deleted all of the ones whose function I fully understand, and left the ones I am still a little (or a lot) confused about. Pin Name Pin function Description 2 CSN Digital Input SPI Chip Select 3 SCK Digital Input SPI Clock 4 MOSI Digital Input SPI Slave Data Input 5 MISO Digital Output SPI Slave Data Output, with tri-state option 6 IRQ Digital Output Maskable interrupt pin 11 VDD_PA Power Output Power Supply (+1.8V) to Power Amplifier 16 IREF Analog Input Reference current 19 DVDD Power Output Positive Digital Supply output for de-coupling purposes These are my guesses as to what the pins are for, please tell me if I am right. 2 CSN Digital Input SPI Chip Select - 3 SCK Digital Input SPI Clock - Obviously something with the clock, but what is inputted here? 4 MOSI Digital Input SPI Slave Data Input - My guess is that its that data you want sent out 5 MISO Digital Output SPI Slave Data Output, with tri-state option - My guess is its the data received by the transceiver 6 IRQ Digital Output Maskable interrupt pin - What is an interrupt? I've never understood that 11 VDD_PA Power Output Power Supply (+1.8V) to Power Amplifier - 16 IREF Analog Input Reference current - I know what it is, but whats it for? 19 DVDD Power Output Positive Digital Supply output for de-coupling purposes - What's de-coupling? Thanks SO much for your help. I'm trying to learn more about electronics, but I can't find good explanations for things, especially terms. Thanks for all your time and help.
  8. Ok, thanks. That's what I wanted to know. I have a few more questions. The datasheet says to use a resistor to ground the "ground" pin of the chip. What is the purpose of this resistor and how would I determine the value of it? The datasheet's example schematic also shows that you should use a bunch of capacitors in a certain configuration around the the antenna pins and the antenna (see the datasheet). In general, what are all those capacitors for, and again, how would I determine their values? Last question. How would I determine what crystal to use with the chip (see datasheet)? Thank you so much for your help. ;D
  9. I know about the length of the antenna already, and that is no problem. The antenna will be hooked directly to the board, so there will be no cable going from the board to the antenna. My question is though, for the antenna, will my thin metal wire antenna that is already on the car work ok? It is stiff, so it stands straight up by itself (it bends back when you drive, but that's a given). My other option is to use a piece of wire that is the right length. Obviously, it will not be stiff or stand up, but I could probably use a plastic tube like a lot of RC cars use to hold up their wire antennas. So either my stiff metal wire antenna or just a piece of wire (not bare wire) that is the right length will work, right? Thanks.
  10. The transmitter's antenna will definetely be vertical. As for the receiver, the metal antenna is vertical, so if I could use that, things would work well. Otherwise I could just use a wire and somehow make that stand up. Whatever I do, both the antenna on the transmitter and the one on the receiver will be standing up. It would work to use just a wire, right? I don't necessarily need a special RP-SMA antenna on the receiver. They use plain wires (obviously insulated wire) all the time in RC, so it should be no problem, right? Thanks for your help.
  11. That's ok. I was planning on that anyway. I figured I would just send the values as numbers (from 0 to 255?) and then convert them back to the right pulse width at the end. It shouldn't be that hard, so I'm not worried about it. Now all I need to do is wait until they get those in stock. One question though. On the receiver side, I will need an antenna other than the RP-SMA (I think that's the right combination of letters) antenna. I will need to use either the thin metal wire antenna the car already has (it can be cut shorter), or a ceramic antenna. Do you think I could somehow accomplish that with the module (preferrably the thin metal wire antenna)? Thanks.
  12. I was thinking of using this to "upgrade" a radio-controlled car with a better radio system for fun. It uses interchangeable crystals in the 27 mhz range, so that's why I said I wanted that. However, after looking into it, I decided it might be wiser to go with 2.4 ghz, as that seems to be the easiest way. I found some neat little chips that you may have heard of. They are nRF24L01 chips from Nordic Semiconductors. Here is a link: http://www.nvlsi.no/index.cfm?obj=product&act=display&pro=89 They seem to have tons of features and are very cheap (a few bucks) and require very few external parts. I am thinking about buying some and playing around with them. Right now, I would like to get a simple two unit test thing going where one unit would send a number or something to the other unit, and the other unit would turn an LED on or off or something. That's what I would like to accomplish right now: something very simple just so I can learn how to do it. Actually, I don't really have a good way to use a chip like that because I have no way to connect to the pins. So while I was looking around I found this: http://www.sparkfun.com/commerce/product_info.php?products_id=705 It's perfect for what I need. It is a simple tranceiver module using the chip I mentioned earlier. It has eight easy connections and an antenna jack. Its basically exactly what I was originally looking for, only it is 2.4 ghz and it doesn't have a crystal socket (not even necessary or possible). If I got two module and two antennae (antennas?), I would be able to easily conduct the tests I want. Its supposed to have a range of up to 80 meters, which is plenty even for when I use it in my radio-controlled car (if I ever get that far). What are your opinions on this module?
  13. What I need for my project is some simple RF transcievers. Here is a list of the things they need to have/do: -Crystal socket for XTAL crystals in the 27 mhz range -4 simple pins/connections: positive, negative, data to send, data received -Place to solder antenna to (obviously) -Small (2x2 inches MAX) -Range of a few hundred feet (at least 100 ft) All of the data sent and received will be processed externally by microcontrollers. All I need the trancievers for is to "convert" electric pulses (my data) to RF and vice versa. They will serve as the wireless link between two circuits (obviously). They need to do nothing more. I simply want to hook them up to power. Then I will have a microcontroller that sends a series of pulses to the pin/connection for data to be sent, and the tranciever will send the data via RF. The same will happen for incoming data. The tranciever will pick up the RF signal and will convert it to electric pulses, and the microcontroller will read this data by connecting to the pin/connection for data received. The quantity, frequency, etc. of pulses will be controlled entirely by external microcontrollers. The trancievers need to do nothing but send the data the microcontroller gives and receive the data it picks up via RF. They need to be that simple. My question is, what trancievers fit this decription and cost very little (less than $10 a piece, preferrably a few bucks a piece)? Where could I get those trancievers? Thank you so much for the help.
  14. Sorry about reviving such an old topic, but I just became interested in this again and would like to continue working on it. I find some ultrasonic transducers here: http://www.sparkfun.com/commerce/product_info.php?products_id=253. Will these work? The are just under an inch in diameter, so they are definetely small enough. They are pretty cheap too, so if they will work then I am going to purchase some. For right now I just want to be able to calculate distance using two circuits. One sends out a signal by ultrasonic means and waits for a response. We'll call this "A". Circuit "B" will wait for a signal and send a response of some kind. When "A" receives a response to its signal, it will calculate the distance based on how long it took to receive a response. Can some please help me on some very simple circuit designs for this? In circuit "A", all I want to do is send a pulse from a microcontroller to the transducer, and then have the microcontroller wait for the response. In circuit "B", all I need to do is have a microcontroller wait for an ultrasonic signal from circuit "A", and then send a response. It should be very simple. I know how to write the code, I just need to know if there are any other parts I will need to use other than the microcontroller and transducer in each circuit. By the way, I will be using a PIC12F675 in each circuit, since that is all I have right now. Thanks so much for the help.
  15. Thanks for the idea. I'll keep that in mind, but I'm going for the easiest way, so if the ultrasonic way works, I will probably go with that. I'm open for all suggestions and ideas, though.
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