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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Timer circuit
I want to build a timer, limited to 5 hrs, for my NiCad charger which runs
on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? |
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"Martik" schreef in bericht news:Qk_Hd.133257$KO5.128773@clgrps13... I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Five hours is much too long for a standard 555 IC. You'd better buy a time switch. The simple mechanical ones can be set by the quarter. Switch it on by hand and place an off stop only at the time you want to swich off. petrus bitbyter |
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On Fri, 21 Jan 2005 03:06:24 GMT, "Martik" wrote:
I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Why not just use an appliance timer? Not the most high tech, but quite effective. See Red Scholefield's "R/C Battery Clinic" for lots of great info on batteries and charging. http://www.rcbatteryclinic.com Alan Harriman |
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Problem is I have to keep changing the stop time, I've seen timers that have
fixed times like 1 2 3 hours but they are $25 "Alan Harriman" wrote in message ... On Fri, 21 Jan 2005 03:06:24 GMT, "Martik" wrote: I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Why not just use an appliance timer? Not the most high tech, but quite effective. See Red Scholefield's "R/C Battery Clinic" for lots of great info on batteries and charging. http://www.rcbatteryclinic.com Alan Harriman |
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buy one a 24 hour normal plug in timer with pins you move, take out the on
pins and only put a off pin at the required time Kevin "Martik" wrote in message news:X43Id.133364$KO5.56248@clgrps13... Problem is I have to keep changing the stop time, I've seen timers that have fixed times like 1 2 3 hours but they are $25 "Alan Harriman" wrote in message ... On Fri, 21 Jan 2005 03:06:24 GMT, "Martik" wrote: I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Why not just use an appliance timer? Not the most high tech, but quite effective. See Red Scholefield's "R/C Battery Clinic" for lots of great info on batteries and charging. http://www.rcbatteryclinic.com Alan Harriman |
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"Martik" wrote in message news:X43Id.133364$KO5.56248@clgrps13... Problem is I have to keep changing the stop time, I've seen timers that have fixed times like 1 2 3 hours but they are $25 I got one that has little pins to select on and off to the half hour. It was free after rebate. N |
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"Martik" wrote in message news:X43Id.133364$KO5.56248@clgrps13... Problem is I have to keep changing the stop time, I've seen timers that have fixed times like 1 2 3 hours but they are $25 "Alan Harriman" wrote in message ... On Fri, 21 Jan 2005 03:06:24 GMT, "Martik" wrote: I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Why not just use an appliance timer? Not the most high tech, but quite effective. See Red Scholefield's "R/C Battery Clinic" for lots of great info on batteries and charging. http://www.rcbatteryclinic.com Alan Harriman Wiring a 555 timer circuit to a relay is trivial, just use a small transistor like a 2N2222 and connect the output of the 555 through a resistor to the base, ground the emitter, connect the collector to one side of the relay coil and connect the other side of the coil to the power supply for the timer. A diode backwards across the coil to absorb spikes is a good idea too. You can also get solid state relays that you should be able to drive directly from the output pin of a 555. |
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"James Sweet" wrote in message news:q5lId.13625$IP6.12567@trnddc05... "Martik" wrote in message news:X43Id.133364$KO5.56248@clgrps13... Problem is I have to keep changing the stop time, I've seen timers that have fixed times like 1 2 3 hours but they are $25 "Alan Harriman" wrote in message ... On Fri, 21 Jan 2005 03:06:24 GMT, "Martik" wrote: I want to build a timer, limited to 5 hrs, for my NiCad charger which runs on 120VAC. I understand that a 555 IC and a properly sized capacitor and resistor will provide the timing. How do I connect this to AC? Relay? Anyone have a schematic? Maybe it would be easier to build a decent charger that won't damage the batteries? Why not just use an appliance timer? Not the most high tech, but quite effective. See Red Scholefield's "R/C Battery Clinic" for lots of great info on batteries and charging. http://www.rcbatteryclinic.com Alan Harriman Wiring a 555 timer circuit to a relay is trivial, just use a small transistor like a 2N2222 and connect the output of the 555 through a resistor to the base, ground the emitter, connect the collector to one side of the relay coil and connect the other side of the coil to the power supply for the timer. A diode backwards across the coil to absorb spikes is a good idea too. You can also get solid state relays that you should be able to drive directly from the output pin of a 555. Thanks, I'll check it out |
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