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  3. For electronics pats sourcing, you can check on digikey or mouser. Also you can ask Makerfabs to sourcing electronics components for you.
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  5. Your 0.33 ohm resistor R7 with 2A in it has a voltage across it of 0.33 x 2= 0.66V. The current-setting circuit in the 30V/3A power supply has 0.47 ohms x 3A= 1.41V across it. Your current-setting circuit needs to be calculated to show 2A when its pot is set near maximum. Only one R7 is used (not two in parallel).
  6. Consider using this: "DC-DC Converter 3V-5V Output Step Up Step down Buck Boost 300V-1200V PSU Module" https://www.ebay.com/itm/DC-DC-Converter-3V-5V-Output-Step-Up-Step-down-Buck-Boost-300V-1200V-PSU-Module/264035829269?_trkparms=aid%3D1110001%26algo%3DSPLICE.SIM%26ao%3D1%26asc%3D20131231084308%26meid%3D303593509b5d4479a35466a0cb15c884%26pid%3D100010%26rk%3D11%26rkt%3D12%26sd%3D174073965556%26itm%3D264035829269%26pmt%3D1%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100010.m2109 If one monitored the capacitor voltage so when it got charged the battery was switched off and back on when it got low the average current drain on the battery would be acceptable perhaps. One could use JFETs and large (mega-ohm resistors) so the drain would be low on the capacitor. The converter would be switched on and off as it charged and recharged the capacitor; so the average current draw would be acceptable. Someone who knows JFETs better than I would be helpful here.
  7. Okay, how about the current sense resistor? For my "30V, 2A power supply" circuit it uses 0.33 ohm 2W resistor for sensing, but your circuit used 0,47 ohm 5W resistor for its sensing purposes. Is there any difference that may affect if I change my 'current sense' resistor with 0,47 ohm 5W like yours?
  8. In the test BQ76PL536PAPT sampling process, it is found that when a channel inputs a signal with periodic interference, the BQ sampling is abnormal. We superimpose a 1KHz peak-to-peak 5V square wave into the BQ sampling circuit, which will act on the CELL2 channel equalization MOS tube to achieve periodic changes in the input voltage. Finally, a triangular wave with a period of about 17s is obtained. I don't know where the problem is.
  9. The following circuit shows a simple circuit to charge a cap to e.g.100-200v. This is for a wild life camera.The main requirement is low quiescent current, less than mA, by the primary side, after the flash capacitor is charged because the circuit operated by battery. Is there a simple solution for oscillator driver, preferably based on transistor, to this problem?
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  11. Choosing the right Surface Finish for Chip on Board assembly is crucial. One of the most frequent questions we are asked at KingCredie Technologies is how should my PCB be plated in order to ensure wire bond-ability. PCB Plating for Chip on Board Assembly must be planned in advance to ensure manufacturability of the device. This planning begins with design rules and selecting the wire bond method to be used. Common wire bond materials include aluminum or gold wire. Aluminum Wedge Wire Bonding and ENIG Plating One of the most common wire bond methods for COB assembly is aluminum wire bonding. For aluminum wire bonding to a PCB the plating can be a low cost method known as ENIG or Electroless Nickel with Immersion Gold. With ENIG plating a PCB with Copper traces is plated with a Nickel layer and then the nickel layer has a flash gold layer on top. The Flash Gold is a barrier layer to protect the Nickel from oxidation. The wire bonding connection is actually from the aluminum wire to the Nickel plating. The main advantage of this method is inexpensive plating and relatively easy wire bonding. The disadvantage is Aluminum wire bonding is less flexible than gold bonding and generally requires larger bond pad pitch compared to gold bonding. Gold Ball Wire Bonding and soft gold plating For Gold Ball Bonding to Printed Circuit Boards a thick layer of soft gold has traditionally been required. In this Case the copper traces on the PCB are plated with a nickel layer and then a soft gold layer measuring between 15 and 30 micro-inches. The gold is electroplated and when plated correctly provides an excellent surface for wire bonding. This method has the advantage allowing for fine pitch gold ball bonding. The disadvantages are high cost and the thick gold layer can cause reliability problems with surface mounted components due to gold dissolution into the solder. Gold Ball Wire Bonding with ENEPEG plating In recent years Electroless Nickel, Electroless Palladium, Immersion Gold plating has been proven to be the best compromise between cost and manufacturability. This method of plating is known and ENEPIG and is common referred to as the universal plating method. It is called universal plating because it offers good wire bond ability and good solder ability. It is suitable for RoHS solders as well as Eutectic SnPb solder. The typical plating thickness is 100 to 150 micro inches of nickel followed by 4 – 10 micro inches of palladium followed by 1-2 micro inches of gold. ENEPIG is suitable for both Gold and Aluminum wire bonding. Additionally, With recent increases in the price of gold price to levels above US$1200 per troy oz, the production cost of electronic device that required thick gold electroplating becomes extremely difficult to control. Since the cost of palladium metal has remained relatively low in comparison to gold, an opportunity for cost saving by replacement of gold with palladium is now available. At KingCredie for PCB plating with Chip on Board we recommend using ENEPIG as a preferred plating method.For more information,tell us what you want to know.
  12. most used electronic components have:Switches,DIODES,Resistors,capacitors,I can buy it here:https://www.electronic-components.hk/catalog/capacitors_cid2001597.html
  13. I will recommend the best e-site for you:www.electronic-components.hk
  14. It's a Multilayer Ceramic Capacitor MLCC - SMD/SMT 0.22 uF 50V 0603 https://gr.mouser.com/ProductDetail/Murata-Electronics/GCJ188R91H224KA01D?qs=QzBtWTOodeUBgk6Gsyvq%2FA%3D%3D
  15. On November 20, SimScale will offer a free webinar to teach everything about resistance network modelling and how to find the resistance values with a detailed model. Thermal resistance network models represent the complex characteristics of an electrical component in a simple form that can be used to carry out thermal analysis in many ways. We can also use thermal resistance models in CFD to obtain better results without adding excessive complexity to the simulation. Learn how to use cloud-based simulation with SimScale for thermal modelling. A professional simulation project will be provided to follow along during the webinar! Participants will also receive the recording via email, so if the timezone does not suit you, it is still worth registering :) Register here: https://bit.ly/2QhSVNf Hope to see many of you there!
  16. GCJ188R91H224KA01D I want to find this part, where is it?
  17. The buyer should be aware of the quality of the product because many companies are providing the duplicate product at such a cheap rate which is very harmful to users. ]If you want the best quality rigid-flex boards, then I would like to refer you to Capel Technology Co,.Ltd , They provide the best product at a very reasonable price.
  18. I recently found several good electronic components sites: Http://www.hotenda.com; Https://electronic-components.hk; Https://www.omo-ic.com; You can buy many rare models.
  19. R7 has nothing to do with the output transistors. Instead R7 senses the amount of output current and sends its sensing voltage to the current adjustment opamp. Each of your output transistors need a series 0.33 ohm emitter resistor so that the two transistors are better matched to share the heating.
  20. Hi! I'm planning on making a electric bobbin winder for my wife for christmas. There are electric bobbin winders on the market, however, they are quite expensive and I'm not impressed with the quality of existing products. I especially do not like the noise output of the existing products. One example of such a bobbin winder is the following: https://www.youtube.com/watch?v=gBp4xZoidVM My idea is as follows: I wish to use the electric mains to power the bobbin winder (220-240V AC) I need a transformer I want a quiet motor, with low maintenance and long lifespan I will use a brushless motor I do not wish to use a gear system - I want to keep this project as minimal as possible. The bobbin winder should be directly connected to the shaft of the electric motor. The speed of the bobbin winder is equal to the output of the motor. I need a motor which accurately is able to do a wide range of RPMs. Prefferably from around 30 rpm - 7000 rpm I wish to reduce or eliminate the amount of programming and components I'm thinking of using a ESC with a single potentiometer input So, here are my questions: What electronic components do I need? (Motor, potentiometer, ESC, power supply, transformator, ...?) Are there ESCs that simply take the input of a potentiometer? Should I choose a brushless motor with a large number of poles to get a smooth running machine on low RPMs? Should I choose a motor with sensor to enable accurate speed control? What specs should my components have? In advance, thanks for any replies!
  21. The old circuit I posted above have included the resistor for the emitter of TR3 (you can see the red marking I made). Should I add more emitter resistor for this output transistor and for the newly added transistor? This is the new design I've made from the old previous circuit. Please take a look.
  22. The parallel transistors in the circuit you posted do not have series emitter resistors so the ones with high gain take a high current and the ones with a low gain take a low current. Emitter resistors help to match the transistors. This is how the output transistors are connected in parallel:
  23. The datasheet of the ULN2003 shows that the saturation voltage loss is 1.4V. Then if the battery is 3.7v the motor gets only 2.3v but if the battery is 7.4V then the motor gets 6V. You did not say how much voltage and current the motor needs. You did not say what is the stalled current of the motor. Stalled is when something stops the motor from turning, which happens the moment it is powered. If the stalled current is higher than 1A (two ULN2003 outputs in parallel) then the ULN2003 will burn out.
  24. I want to make a car, use the driver module, just have a piece of ULN2003 on hand, just think about whether you can use this chip to drive, check the DATASHEET, the current of each port is 500mA, I use the two ports in parallel Do a mouth control 1 motor, a total of 4 ports control 2 motors, the battery uses two 3.7 lithium batteries, do not know if this chip can work very well?
  25. I have no idea how the parallelized transistors look like. My friends told me to use darlington-pair for a power transistor. I have a schematic of power transistor parallel-configuration for an inveter, here's the picture: Sorry for asking this, but can you show me an example of a parallelized power transistor. Thx in advance
  26. The very old circuit you posted works poorly. TR3 is its output transistor and it gets too hot. Add a second 2N3055 transistor parallel with TR3 to share the heat and add a 0.33 ohms/2W resistor in series with each emitter to the output. The transistors collectors can be connected directly together by the heatsink if the heatsink is insulated from any other part of the circuit. If you want a 0V to -30V, 2mA to 3A power supply then make a second one of this project and use its +30V output as 0V and use its 0V output as 0V to -30V. A center-tapped transformer will produce an AC output, not DC and not variable.
  27. A tiny DC to DC buck converter board is useful for many applications, especially if it could deliver currents up to 3A (2A continuously without heatsink). In this article, we will learn to build a small, efficient, and cheap buck converter circuit. References Full Article: https://www.pcbway.com/blog/technology/DC_to_DC_Buck_Converter_Adjustable__97__Efficient__3A.html MP2315 Library: https://componentsearchengine.com/part.php?partID=930350 Altium Plugin: https://www.samacsys.com/altium-designer-library-instructions
  28. Check the link to get Thomson TV circuit board diagrams, schematics, PDF service manuals
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