Alternating On-Off Switch, #2(link) 2007-08-25 13:28:00 Alternating On-Off Switch, #2(link)This circuit is the transistor version of the 4069 cmos type. Every press of the push-button will activate or de-activate the relay.
The Boost Regulator Switching 2007-07-21 11:30:00 In a forward (or buck) regulator power is continuously supplied to the outletfilter capacitor. In a boost regulator, however, energy is pumped in a cyclic manner. The filter capacitor therefore has to be of a higher value. The boost regulator, like the flyback regulator, pumps energy into the outletfilter capacitor in a cyclic manner, and it is therefore desirable to operate in the discontinuous mode with a fixed peak current through the inductor. The diode conduction time in a boost regulator, unlike the flyback regulator, is not fixed, but varies with the input voltage.Ipk = 2 x Iout,max x (Vout / Vin,min)Tdon = (L x Ipk) / (Vout - Vin)Output voltage is regulated by controlling the duty cycle.Vout = ((Ton / Tdon) + 1) x VinRipple voltage is directly proportional to diode conduction time.Tdon max = (L x Ipk) / (Vout - Vin,max)Source : http://www.hills2.u-net.com/electron/smps.htm Read more:Boost
, Regulator
, Switching
Switch Mode Power Supplies. 2007-07-21 11:28:00 Introduction - Some Definitions. Switch Mode Power Supplies are the current state of the art in high efficiency power supplies. Conventional series-regulated linear power supplies maintain a constant voltage by varying their resistance to cope with input voltage changes or load current demand changes. The linear regulator can, therefore, tend to be very inefficient. The switch mode power supply, however, uses a high frequency switch (in practice a transistor) with varying duty cycle to maintain the output voltage. The output voltage variations caused by the switching are filtered out by an LC filter. SMPSs can be used to step-down a supply voltage, just as linear supplies do. Unlike a linear regulator, however, an SMPS can also provide a step-up function and an inverted output function. Typical applications are given below. Typical application for a ste-down switching regulator: Generation of 5V for TTL-based circuits from a 12V battery (particularly suitable if the 12V batte
40 Hours of Play for those Long-Haul Flights 2007-07-21 11:24:00 To prepare for the trip, we looked online for the biggest most long-lasting PSP battery pack we could find. Imagine our disappointment! We couldn't find any that went beyond about 8 hours of play time. This is no use on a 22-hour flight. I found myself wondering why they didn't just make a PSP battery pack that could take normal batteries that you can buy at any airport. Sure, it would cost a bit to run on Duracells, but it would solve the problem of PSP power on a long flight once and for all. I seemed to recall that Duracell 'D' cells store about 12,000mAh (compared to the PSP internal battery's puny 1800mAh). And thus, the concept for the PSP Power Brick was born.Read more Read more:Hours
SERIES REGULATED 4.5 TO 25 VOLT, 2.5 AMP POWER SUPPLY 2007-07-16 23:54:00 SERIES REGULATED 4.5 TO 25 VOLT, 2.5 AMP POWER SUPPLYARRL HB 93 CHP 27 FIG 22 95HB FIG.11.32 Description: This is a variable voltage and adjustable current limit power supply project.
Regulated Power Supply 13.8VDC 2007-07-16 23:47:00 Regulated 13.8V DC Power Supplies.Output short circuit protection with current limiting.Overvoltage protection with internal fuse. Read more:Supply
High Current 13.8V Power Supply 2007-07-16 23:42:00 High Current
13.8V Power Supply
Rod Elliott (ESP)There is absolutely nothing special about the circuit, except that as shown, it is quite capable of up to 20 Amps intermittently or 10A continuous. Read more:Power Supply
10 Amp 13.8 Volt Power Supply 2007-07-16 23:36:00 10 Amp 13.8 Volt Power Supply
source: By N1HFX Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers.
VHF-HF TRANSVERTER 2007-07-11 08:27:00 This little circuit is a transmitting and receiving converter (transverter) that converts a FT290 or similar multimode handheld transciever to the 14MHz amateur band. The project is a single board module that needs an external local oscillator, for example, the VHF harmonic oscillator (or QRP VHF FM TX) LO for transverter project. It should be a relatively simple matter of scaling coils and caps to convert other bands. You may choose to omit the TX/RX switching and the TX mixer and use this unit as a receive converter giving 14MHz - 16MHz coverage on a multimode VHF receiver. If you choose to use the full transverter circuit then you will be pleasantly surprised at the spectral purity of the transmitted signals. All unwanted spurious signals and even oscillator breakthrough are well under -75dB at the output terminal. The HF TX output from the unit is about 2mW and will give a full ten watts from my 10-Watt HF linear amplifier. The VHF rig must be of the type that also delivers +10v
power supply 0-15V 5A 2007-07-11 08:15:00 Here is a rather novel Power Supply Unit (PSU) for the workbench which can deliver 0-15 volts and up to 0-3 amperes. I have not shown any mains fuses as this I will leave to your own devices. You should as a minimum have a fuse in the primary and secondary of T1. The circuit is a little cramped, but this is because I will also be posting the circuit to QRP@WW on the packet radio system. There are two resistors in the circuit marked "*see text" and these set the maximum output current limiter to a suitable value. Omit the 0R2 resistor and the PSU will deliver 100mA maximum. In this event the output TR8 can be almost any medium power
transistor such as the 2N3053, BFY51 etc. It must be mounted on a heatsink no matter what output you need. The 6R8 resistor may be an ordinary 1/4 watt resistor and is used on all versions of the PSU. The additional 0R2 (0.2 ohms) sets the maximum current limiting to about 3 amperes. If you only want a 0-1 ampere PSU then use 0.68 ohms. T1 is
DC13.8V to DC250V easy circuit 2007-07-11 07:56:00 I have done a lot of work with valves in recent years. For me valves have many advantages, least of all the price; since they are now "obsolete" it is quite easy to get hold of them for next to nothing at rally's and junk sales. I recently purchased a couple of hundred battery valves for less than SEK1 (US$ 0.15) each. The biggest problem with valves is the PSU needed to provide +250 vDC and 6.3 vAC for the fillaments. The transformers are no-longer available at a reasonable price, but a pair of 12v-6v-0v-6v-12v mains transformers will do the job just as well. For portable use only one transformer is required together with a pair of power transistors such as 2N3055 etc. Above is the circuit of a converter that will generate the required volrages from a 12 volt source. Above is the circuit of a converter that will generate the required volrages from 220 volt mains. Just one word of warning: Dont forget to put a "bleeder" 100K - 270K ohm resistor accross the 250vDC output if your equi
Zinc-Carbon Battery charger 2007-07-11 07:08:00 They are cheap. The electrolyte used to leak but today they are usually much better protected. If they should leak then they will corrode all the copper in your equipment. the corrosion will travel down wires and eat its way through Printed Circuit Boards (PCBs). At high temperatures (25 degrees or more) Zinc-Carbon
batteries will give up to 25% more capacity but the shelf-life will deteriorate very rapidly. Around freezing point their shelf-life can be extended by as much as 300% so one tip is to store them in the refrigerator. Unfortunately they must be thrown away when they are exhausted. You can extend their life by up to 60% by using "Dirty-DC" to recharge them but this will also reduce the shelf-life. Ry should be about 1.5 x greater than Rx. The resistors are determined by the charging current you want. With the circuit shown and size AA cells in a pack of ten cells, the battery voltage will be 15 volts. Discharge the battery to no less than 25%. To replace 350mA
Digital Step Km Counter Max 2007-09-03 03:59:00 Digital Step Km Counter
Max.: Pedometer has a range of 9.950 meters with2-digits. Slip it in pants pocket for walking and jogging Read more:Digital
Pedometer 2007-09-03 03:57:00 Pedometer: Pedometer has a range of 9.950 meters with2-digits. Slip it in pants pocket for walking and jogging
Tiny tiny invertor design 2007-10-23 20:22:00 Tiny tiny invertor design
- run off of 3V, and charges up a little 1 uf 250V cap all the way up in about 30 seconds
Pulse Generator Schematic 2007-10-23 20:21:00 Pulse Generator
Schematic - Can be used to evaluate high voltage pulse characteristics of zeners and MOV's Read more:Pulse
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