| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 61716 | 2005-09-14 06:36:00 | Central locking | george12 (7) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 388398 | 2005-09-16 03:34:00 | Mm... Got the door cover off but it's very hard to get at the actuator. Anyway I popped down to Jaycar and bought a "Master" actuator with microswitch outputs, but I DO need the permanent -> momentary timer, because it's just locked = one wire grounded, unlocked = another wire grounded. Hooking it straight up would try to constantly lock or unlock, probably burning out the actuators. I'm scouring for a circuit that will do it. Basically, what I want is when something is grounded, and stays grounded, for the output to be grounded for about half a second. |
george12 (7) | ||
| 388399 | 2005-09-16 03:39:00 | The circuit here (home.cogeco.ca) (very bottom) is perfect except the output is positive, and I need the output to pull down to ground. Transistor? Relay? | george12 (7) | ||
| 388400 | 2005-09-16 03:51:00 | A transistor will pull down to within about 0.6V of ground, a relay will go to ground. But a transistor will usually be close enough. Use an NPN (BC548..9). Just a 1k to the base, the emitter to ground, and the collector to output (with a pullup resistor if needed). Or go back to the PicAxe. | Graham L (2) | ||
| 388401 | 2005-09-16 04:10:00 | It's gonna run off a laptop (linux of course), so I can unlock the car via bluetoothing a 10-digit code to it, and I will have a fingerprint scanner in place of the keyholes. Unlocking either of these ways will automatically shift it to neutral, unlock all doors and start the engine, warming it up for me, all before I even get up out of bed. Then when the engine is started, it will run through a list of routines (as I begin to wake up) including squirting water on the windows and cleaning them, defrosting front and rear (if the temperature is appropriate), and warming the interior of the car. It will text my cellphone via the internet to politely remind me to get up, and that the car is ready. When I get down there, most likely at about 8:30, it will be warmed up and ready for a speedy takeoff, because by that time I'll be most likely late for school. now this is some ub3r g33k tech :thumbs: |
Prescott (11) | ||
| 388402 | 2005-09-16 09:57:00 | A transistor will pull down to within about 0.6V of ground, a relay will go to ground. But a transistor will usually be close enough. Use an NPN (BC548..9). Just a 1k to the base, the emitter to ground, and the collector to output (with a pullup resistor if needed). Or go back to the PicAxe. Two questions: 1) Can a 555's output drive a relay directly? If so I'll do that. 2) What goes on the other end of the "1K to base", and which output does the collector go to - the output to the relay box or the output of the timer circuit? |
george12 (7) | ||
| 388403 | 2005-09-17 02:27:00 | 1) A "standard" 555 will drive a small relay (about 200-300 mA sink or source). The CMOS version (7555?) is much less grunty. I don't know off hand how much less. 2) Think about it. You have a signal which is low then goes high momentarily. That's your 555 pin 3? you want to invert it. So you feed that to the input of a transistor -- the base -- through a resistor to limit the current. When the base goes high, current flows through the transistor to the emitter, which you have grounded. This turns on the collector-emitter junction, fairly hard -- "saturating" -- so the collector will be pulled down near ground. So you connect the collector (the transistor's output ion this "common-emitter configuration) to the point you want to be momentarily pulled low. If that point has a voltage on it, that's all you need. If it needs to have a voltage applied to it, do that with a resistor to the supply you are using. That would be the "pullup". |
Graham L (2) | ||
| 388404 | 2005-09-17 05:06:00 | Exxxxcellent. Thanks very much Graham. I'll pop down to Dick Smith when my parents vote and buy all that. A transistor sound the best way I think. Cheers |
george12 (7) | ||
| 388405 | 2005-09-17 09:59:00 | heh...tried some big stuff with picaxes...they ok but not powerful...:) i wouldnt use bluetooth,personally,because its very easy to crack... try an ibutton,they are a lot more difficult to break,and they are waterproof too... oh,and maxim will send you 2 as free samples...;)... they use a 1 wire bus,and the picaxes will read em(bout the only thing they really good at...) as to the cct one shot monostable?the answer is so simple you will kick yourself when you figure it out...and you wont need anything else to do it...;) |
satanx (8009) | ||
| 388406 | 2005-09-17 11:01:00 | heh...tried some big stuff with picaxes...they ok but not powerful...:) i wouldnt use bluetooth,personally,because its very easy to crack... try an ibutton,they are a lot more difficult to break,and they are waterproof too... oh,and maxim will send you 2 as free samples...;)... they use a 1 wire bus,and the picaxes will read em(bout the only thing they really good at...) as to the cct one shot monostable?the answer is so simple you will kick yourself when you figure it out...and you wont need anything else to do it...;) Exactly what I'm doing. Thanks for the help everyone. |
george12 (7) | ||
| 1 2 | |||||