FGY/BQBO/HPT92656/FGYBQBOHPT92656.MEDIUM.jpg' alt='Arduino Python Serial Mysql Update' title='Arduino Python Serial Mysql Update' />Simple Dual voltage Tracking Power Supply for 3 to 1. Updated 1. 6th May 2. Completed prototype. In a previous post Versatile Dual Power Supply Printed Circuit Board I described a dual power supply design that I hoped would fulfil 9. To this end, it was very successful, and several have been built and installed in various pieces of equipment. These have been mostly of the fixed type of supply, and for types using the LM3. LM3. 37 adjustment of the two presets has not usually been a problem, simply set and forget. Wonderware 7.11 Patch. When, however, a dual supply is require that is continuously variable say, for example a bench supply, the individual adjustment of the presets is a pain. Of course the problem can be partially solved by the use of a dual ganged pot, and judicious use of trimmer resistors, but it is unlikely that such a system will offer precise voltage tracking between and. A better solution would be the use of a single pot to set both voltages simultaneously, and for precision setting this could be of the 1. There are several dual tracking regulators around, but these are generally expensive, and may necessitate special ordering. I present here a reasonably simple solution that substitutes an op amp and a few resistors for the ve control pot, that is suitable for supplies delivering between 3. In a separate post I will discuss simple bootstrapping of the op amp so that the voltage range can be extended upward, and also a power booster for high current use. FUQ/4ODC/IE17WWCZ/FUQ4ODCIE17WWCZ.MEDIUM.jpg' alt='Arduino Python Serial Mysql Update' title='Arduino Python Serial Mysql Update' />Now referring to the two schematics below, it will be seen that they are essentially mirror images of each other. If we remove resistor R2 in the second schematic, and connect the mirror image of the voltage found at the junction of R1 and R2 in the first schematic, full tracking between the ve and ve outputs will be achieved. Now refer to the third schematic, drawn by me, in which Ive combined the two circuits below, and added in the mirror image voltage generator. LM3. 17 base PSU unashamedly stolen from Texas Datasheet. LM3. 37 based PSU design also stolen this time from National Semiconductor Datasheet. Dual Voltage Tracking PSUIn the above, IC1, R2 and R7 comprise an amplifier with a gain of 1. Put simply, any positive voltage appearing at the ADJ terminal of the upper LM3. ADJ terminal of the lower LM3. The net result is control over both outputs achieved with the single adjustment pot R1. We call our project RUFS, for Robotic Urban Farm System A vertical hydroponic garden Allowing for high density yields and shorter growth cycles. Arduino Python Serial Mysql Update' title='Arduino Python Serial Mysql Update' />KohmsAs always, the Devil is in the details, and the following should be noted. Firstly the ve and ve supply for the op amp IC1 are derived from the ve and ve outputs themselves this may seem strange, but has been done for the following reason. Using the monolithic op amp TL0. This would mean that if the op amp supplies were derived from the raw DC inputs, the IN terminal of each regulator some way of ensuring this never exceeded 1. Far simpler is to set the absolute maximum output voltage to around 1. This is achieved by placing a 6. K ohm R1. 0 resistor across the adjustment pot R1, so that the largest value of the combined paralleled resistors is around 2. K. Since there is always a voltage drop of around 1. R3, this allows the op amp to control a full range from around 3 volts to 1. Ems Iso 14001 Manual Examples. PNG' alt='Arduino Python Serial Mysql Update' title='Arduino Python Serial Mysql Update' />Although not essential, without the offset adjustment trimmer R8, the voltages will track to within a tenth of a volt or so. Inclusion and set up of R8 and R9 will allow tracking accuracy to within a few hundredths of a volt. High stability 1 tolerance metal film resistors should be used for R2, R3, R4, R7, and R1. Other resistors are 5. Testing. Setting up is simple. Set R8 to its mid position, then set the voltage adjustment pot so that 1. KpX80cpa7Tc/Vp5xAMAqbLI/AAAAAAAAAG8/EUHCNJM_1MQ/s1600/conn_ard.tiff' alt='Arduino Python Serial Mysql Update' title='Arduino Python Serial Mysql Update' />IC2. With a voltmeter on the output of IC3, adjust R8 so that the obtained voltage is the exact mirror of that obtained at the output of IC2, i. Tracking should be maintained within a few hundredths of a volts throughout the range 3. During testing, the following was observed. I discovered a very low level parasitic oscillation at the output of IC1 on the 1st version of the PCB. Adding a 4. 7p. F capacitor C1. R7 cured this, and the Schematic and Board reflect this small addition. With an ambient air temperature TAMB of around 1. C, the op amp IC1 warms up slightly. With the circuit supplying 1. I affixed a temperature probe and left things to stabilize for around 1. C. As is usual with observations, the method of measurement has a quantum like effect, and I attribute some of this temperature rise to the fact I had to tape the probe onto the op amp case, affording it some insulation from free air. I checked drop out voltages by supplying the unit from a VARIAC. The results were as follows, and were what I expected Construction. Images of the PCB foil and component layouts are given below. The Downloads section has links to the Eagle project files. Dual Tracking PSU PCB Foil side. Dual Tracking PSU PCB Component layout. UPDATE 20151115 This post is obsolete and out of date. Current best practice is according to pip is to use the following python m pip install U pip setuptools. Responses to New smart meter installed Iskra ME382 and Landis Gyr gasmeter E06140. The prototype PSU during testing. Top view of completed prototype. Verifying calibrated voltages. A front panel. I used Front. Designer to put together a front panel for the PSU. Sods Law states that if something can go wrong it will, and because of the design, the voltage control is roughly anti logarithmic. Front. Designer only caters for linear and logarithmic scales, so I plumped for a linear scale total rotation 3. A high definition export of the panel design is available in the downloads section. The Dual PSU front panel. Update 1. 6th May 2. A while ago, I received a helpful comment from Harry Brunt regarding this post, which referred to an article describing a design about which Harry remarked I could omit the need for a trimming resistor and possibly improve the tracking if you include the negative voltage regulator within the negative feedback loop of the op amp. Harry himself has experimented with this design, though sadly the link has gone the way of many others, and is no longer valid. Harry reported that the design worked, but that tracking was not as accurate as he would have liked, and has augmented the schematic, so that tracking within a few millivolts can now be achieved. The design is an interesting alternative to mine, providing as it does, tracked dual supplies down to nearly zero volts, and I have built the circuit and can verify as to Harrys reports on the excellent tracking. I have shown Harrys schematic below. I substituted an LF3. LM1. 08 op amp Harry suggested, as the latter isnt stocked at my local electronics store. I matched the two 1. K 1 resistors to within 1. Other resistor values are not critical, and as Harry suggested, offset trim resistor on the op amp doesnt appear necessary, and wasnt tried. Cartier Chronoflex Manual more. Harry Brunts Dual Tracking PSU Schematic. A zip file containing PDF and jpg of the above schematic is here http joebrown. Dual. PSUfwpsu. End of update. Downloads. The Eagle schematic for the Dual Tracking PSU is here http joebrown. Dual. PSUSplit. SupplyTracking. Dual. PSUSplit. SupplyTracking. The Front. Designer project file is here http joebrown. Dual. PSUDual. Tracking. Variable. PSU. FPLand a high definition exported image file is here http joebrown. Dual. PSUDual. Tracking. Variable. PSUFPL.