For the DLU to operate in a useful manner an efficient method to eliminate the dissipated power must be employed. ¿¿¸ø£QÄÔ,οޢW„)š% Á¦çr¨y³)õÎüu3Ï'{.͂sñ³. We use cookies to ensure that we give you the best experience on our website. Build a simple HF/VHF 100W dummy load Chris G4AKE Every radio amateur should own a dummy load. Required fields are marked *. It is quite easy to get this circuit to oscillate. High Voltage Dummy Load 3000 OHMS, 5400 WATTS There are 45 layers of 6 resistors, each one being 400 OHMS @ 20 Watts for a total of 270 resistors (by W4ZT) A … The first parameter we should defined is the maximum current and voltage that our dummy load will handle. Find 63W point and trace at what degrees the case temperature should be maintained. To make the schematic less cluttered, I had deliberately omitted the filtering capacitors and decoupling capacitors. 5.1. To test real capacity of a power supply, we need a load with variable current consumption. Functional isolation is a really important requirement. For low power 4 ohm tests, you can use any single 4 ohm section (90W each) - take your pick. Therefore, at present maximum 24V, 5A load can be set by this dummy load. PARTS LIST. Save my name, email, and website in this browser for the next time I comment. High Frequency. Great for working on tube amplifiers. Alpha 2100 HF Dummy Load. You can see the digital isolators for the comms on the schematic. For model Dummy-Load-Wattmeter 334A, Waters Inc.; Wayland (MA): Quelle: Bauer-Katalog, Bamberg, 1968 Dummy loads are useful for determining maximum amplifier output power and for "burn-in" of an amplifier under full power for several hours or days to insure reliability before the amplifier is sold to a customer, or returned after a repair. It would be very useful to know how to test a voltage source in order to determine if its characteristics are good or not. The first version (v1.0) of my USB Dummy Load circuit presented here is a cheap and cheerful solution for testing USB chargers and USB power banks/batteries. dummy load is able to finely control how much power the dummy load unit will draw. The analog circuit follow this formua. The files for download: PCB pattern in PDF for printer a soldering plan in Eagle. Check the power dissipation at final transistor, make sure it can handle. if i use this circuit which component should decrease? We have to install a heat sink for the transistor, since the transistors work in linear mode and dissipate a lot of heat. It is submerged in oil to allow somewhat extended operation during tuning or … Variable Dummy Load for Power Supply Testing It is easy to find on the Internet many designs of voltage sources, with which we can power our circuits designs. Figure 2. The dummy speaker load box is reconfigurable to 2-ohm, 4-ohms, 6-ohm, 8-ohm, 16-ohm and 32-ohm loads. The choke or inductor is shunted by a .0004 MFd capacitor in series with a 400 ohm non-inductive resistor. It will provide 6x gain. In radio a dummy antenna is connected to the output of a radio transmitter and electrically simulates an antenna, to allow the transmitter to be adjusted and tested without radiating radio waves. I now have a very nice dummy load: Variable Dummy Load Circuit Schematic Diagram. 4.4. Mechanical Drawings. I have used it up to about 3.4A. This article is a quick guide to building a simple electronic dc load (dummy load) that will be useful for your upcoming power-electronics projects. Cascade the Darlington configuration until we find a small enough wattage to be handled by a cheap potentiometer. Check the base current and voltage to operate at maximum rating by dividing the collector current with the DC current gain of the transistor, choose a suitable transistor to drive in a Darlington configuration, or use a suitable potentiometer and resistor if it small enough. Schematic of a simple dummy load for power supply testing. In this photo, the multimeter shows the dummy load drawing 1.02A from a 5V power supply. let say we choose 1 Ohm, then the wattage will be square of current times the resistance, we get 9 watt, and we can use 10W which is available on the market. Home brew dummy loads category is a curation of 30 web resources on , Building A RF Dummy Load, QRP Power Meter and Dummy Load, RF Dummy Load. The RMA dummy antenna consists of a 0.0002 MFd capacitor that is in series with a 20 uH RF choke. Or run ½ KW CW or 1 KW PEP for 20 minutes. If you continue to use this site we will assume that you are happy with it. 5. Your email address will not be published. Now look at the power derating graph of the final transistor 2N3055. You don't need to pollute the airwaves while just tuning or testing your transmitter! The simple design uses power resistors to insert a load on the USB power lines, imitating an external device drawing a delimited amount of power from the concerned USB port. Don’t like getting wet? A special copper heat sink spreads the heat to a larger set of … Arduino DC Electronic Load Circuit Diagram. The dummy load would act as a speaker so that the power amp would just 'think" it was working normally. i want to build DIY constant current dummy load. A Radio Manufacturers Association(RMA) dummy antenna is a simple device and very easy to construct. This dummy-load circuit has been in use at Maxim for more than 10 years (see the figure).It's useful for testing power supplies and power amplifiers as well as drivers for LEDs, relays, and solenoids. I just finish a simulation using Circuit Wizard. Figure 2 Dummy Load Schematic. We can see a point around 100°C, so we can easily maintain the heatsink temperature by immersing a half of bottom part of the heatsink into water. The RMA antenna sounds more complicated then it really is. Building the Dummy Load. TMC050 wire wound power resistors from Vishay mounted to heatsinks to increase power dissipation are used for the load. The schematic below shows this electronic load design. Here is a simple solution using power transistor. Building The Circuit. Unfortunately, this kind of high power resistor is expensive and not so flexible getting wide adjustment range. It uses a number of non-inductive resistors in parallel to achieve 50 Ohms over a wide frequency range. You can see in the Figure 1  that we use a speaker box terminal to ease the connecting and disconnecting the ampere meter, voltmeter, and the power supply. The load will also be controllable from a PC application as I want to be able to sweep the load current and record the V-I curve. The oscilloscope shows that there are no oscillations, hence the circuit is stable. The dummy load comes complete with a derating curve. A 8 Ohm 100W Non-Inductive Dummy Load Resistor mounted on a heat sink would do the trick I think. Multi-Channel Expansion Oversampling: 15Bit from 12Bit ADC, CD4093 Switch-Mode Current Limiter for LED Driver, Flasher Circuit with DPDT Relay Works for Any-Wattage Load, Adjustable 1-30V Laboratory Power Supply Uses Switching and Digital Control Technology, Modular Fastest Quiz Controller Circuit Using Relays. Alpha 2100 HF Dummy Load. I'm looking for constant current dummy load around 50A use for testing of my power supply 50A 2-5 hrs. 8 Ohm 100W Non-Inductive Dummy Load Resistor 019-020 100% 95% 75% 25% 5% 0%. Resources listed under Dummy Load category belongs to Technical Reference main collection, and get reviewed and rated by amateur radio operators. A common approach is to connect multiple It is OK to left the water boils during few minutes usage. If we have high power variable resistor such as tapped wire-wound resistor, we can directly connect this resistor and make some measurement. Figure 2 - Dummy Load Panel Layout. Alpha 2100 - front folded. PCB pattern and soldering plan, Temsi made according to my schematic (thank you). So, inspired by V1.0 of my Electronic Dummy Load which has 2 amp maximum I thought I'd build a bigger unit capable of up to 10 amps @ 25vdc (250watts). A Darlington pair is used to provide high impedance input since we want to use a low wattage potentiometer to vary the loading. DRAKE DL1000 Modified Dummy load R1 and R2 make up the dummy load resistor Clamp coupling capacitance Added series resistors 0.25 W total Added shielding around main resistor improves SWR Shield to shield shorts VHF Response compensation-Improved SWR, remains low up to 450 MHz-Adds attenuator output (-30 dB and -40 dB with pad) —þ©æʍpåOÈu¾§ü¶¾Ë^\ëz'£ÈñãÙr¨š;>q8÷\ÿ©cÇöð͕£þËó¼Û–ÖÎÎá¤ù~‹t™/ÔÑ^;×ï:nëZ±å3àËÅíîŸLTVh+WÔY\r’´y_´çˆwÃióGk¬ÙäÌ_2Fy.Çן:. Alpha 2100 three boards in front. Watch the video of this assembled dummy load circuit on our Youtube channel below: Your email address will not be published. And until now I've always used just a bare wirewound resistor with some banana plugs as a test load. A dummy load is a device used to simulate an electrical load, usually for testing purposes. Matt shares with us his build of a fantastic looking dummy speaker load box. The MFJ-250 VersaLoad KW Wet Dummy Load lets you tune up fast! The schematic below shows two dummy loads, built into one enclosure. Here is the schematic diagram of the circuit. However, rarely is the one you want to be found! A dummy load is a piece of equipment used in place of a speaker when working on or testing amplifiers. Let’s say that we need a dummy load that can be set to draw maximum of  3A  from 24V power supply. You can check the net load for yourself by following the basic electronics formulas. currently i'm using heater to replace power resistor but the current always drop when the heater generate heat. Alpha 2100 inside. any advise highly apperiate. Oscillations. I also omitted the microcontroller circuitry as it is rather standard. The number of resistors used in the circuit depend on there value & your needed power requirements. SSPJI­05: ELV Dummy Load for PSU Testing The Control Circuit The circuit diagram for the control unit is shown below. In the below schematic, the operational amplifier has two sections. There are a number of solutions for making a simple electronic load – you only have to take a look around the web to see that. Variable Dummy Load Circuit Schematic Diagram. You can use this dummy load to simulate the load on the power supply circuit under different load conditions, to monitor the temperature curve in relation to load. With a speaker connected, the amplifier will see either a 4.3 or 7.4 ohm load while the attached speaker will receive less than about 1% of the output power. The one described here is capable of dissipating 100 Watts for short periods of time and provides a low power 50Ω port suitable for connecting a receiver or spectrum analyser for station monitoring. We have to install a heat sink for the transistor, since the transistors work in linear mode and dissipate a lot of heat. To make the dummy load useful for testing modern amplifiers,it is necessary to provide a choice of at least two load impedances (8 Ω and 4 Ω), and preferably 6 Ω as well, which can cope with power levels comfortably above 100 W for the 8Ω load and somewhat higher for the two lower impedances. Another section of the amplifier is configured as a gain amplifier. The components in the schematic diagram is not so critical. 1 * LM8272 op-amp 2 * IXTK46N50L N-type Mosfet What's needed is an adjustable dummy load, or an Elecronic Dummy Load! Simple Dummy Load Power Meter Simple Dummy Load Power Meter. This Dummy Load Power Meter is very useful for RF power measurements in HF and VHF frequency bands. This is a take-off on a Dummy load that I've built in many different forms over the years. Using D313 as the final transistor will be unsafe since it handle only 3A at maximum. A nice dummy load. In audio systems, a dummy load is connected to the output of an amplifier to electrically simulate a loudspeaker, allowing the … This kind of dummy load is widely used in testing power supply. Choose R2 resistance value. Generally the higher the wattage rating of the resistor the more power the dummy load can safely handle. It is designed to safely dissipate the entire power of the amplifier. Select picture or schematic to display from thumbnails on the right and click for download. Just use a big heatsink and fan! To demonstrate this, we will use a 7805 linear voltage regulator to step the 12V supply down to 5V, and draw an increasing load … As an example the dummy load schematic shown here uses ten 500-Ohm resistors with a power rating of 1-watt each. Use trans I re-do the circuit of your "Dummy Load" circuit, And the circuit can be control be Arduino using a D/A for the 5 V section ( Vin ) and the current monitor, the voltage at the Power resistor can be scale down ( to 5 V ) and going into an analog pin. Use high amperage rating for Sw1, and use a convenient terminals to connect ampere meter, voltmeter, and the tested power supply. It uses a quality 50 Ohm non-inductive resistor. Similar to what guys use to test amps on the workbench without having to plug in a cabinet. Well, no longer! After many requests, here it is, the simple 4 or 8 ohm switchable resistor dummy load. It's a load that has a purely resistive impedance of 50 ohms at all frequencies of interest (HF in my case). The panel layout shown above allows you to use short, stout leads with banana plugs to configure the load, and is an almost exact copy of the one I've used for many years. The dissipates power a transistor is now 3A*21V = 63 watts. Soldering all components (except the transistors) on to a matrix board is the fastest way to build this circuit, it will be very easy because its simplicity. Primitive construction of my variable dummy load without any PCB board :). Run continuous duty with 200 Watts CW or 400 Watts PEP. I've been building audio amplifiers for years. Choose the final transistor that capable of handling the maximum current and voltage, a 2N3055 will be safe since it handle max 60V and 15A. All the connections to the standard Arduino board are clearly marked for easy references. You can run 1KW CW or 2 KW PEP for 10 minutes. ‹Û—ç ¬Þûd¯=9çå6\aΊ3üÖßêHWûÌãUþ With 3 amperes through R2, it means the voltage across R2 is current times the resistance = 3A * 1 Ohm = 3 volts, and the voltage between collector and emitter of final transistor is 24V-3V = 21V. Here some steps to ease the selection process: Update (January 2014): Variable Dummy Load In Action. A dummy load is just one of those standard tools that you need in the shack. Use plain water with a little salt added to build your own Dummy Load (by K5LXP) 5400 W Dummy Load. Soldering all components (except the transistors) on to a matrix board is the fastest way to build this circuit, it will be very easy because its simplicity. Schematics. We use cookies to ensure that we need a load that can be set to draw maximum 3AÂ! Oscilloscope shows that there are no oscillations, hence the circuit is stable in order to if. What 's needed is an adjustable dummy load you continue to use this site we will assume that need. Easy references power supply % 75 % 25 % 5 % 0 % wide adjustment range, we a... To what guys use to test a voltage source in order to determine if its characteristics good. Control how much power the dummy speaker load box is reconfigurable to 2-ohm, 4-ohms, 6-ohm,,. For printer a soldering plan in Eagle less cluttered, I had deliberately omitted the circuitry... 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Take-Off on a dummy load would act as a test load simple dummy load drawing 1.02A from a power. Of heat an example the dummy load resistor mounted on a heat sink for the next time comment... Load will handle ( thank you ) '' it was working normally * LM8272 op-amp 2 * IXTK46N50L Mosfet. Into one enclosure DIY constant current dummy load comes complete with a 20 uH RF choke frequency.: Quelle: Bauer-Katalog, Bamberg, 1968 a nice dummy load unit draw! Schematic to display from thumbnails on the workbench without having to plug in a manner! Bare wirewound resistor with some banana plugs as a speaker so that the power derating of! Amps on the schematic less cluttered, I had deliberately omitted the microcontroller circuitry it! Load unit will draw a 8 ohm switchable resistor dummy load LM8272 op-amp 2 * IXTK46N50L Mosfet.