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| DIY Voltmeter/Ammeter for lab power supply |
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| Simon:
Yes power supplies are a typical first project and a good learning experience but getting the meter right is kind of important. |
| Kleinstein:
Using PWM and linear control of the fan is perfectly fine. However this would likely need a beefier transistor (e.g. BD135 or BCP56 like (SOT223) as there can be quite some heat. To make the linear control work better at least another resistor (e.g. 470 ohms) in front of the base would be a good idea, as it helps filter. |
| Simon:
I know they are old hat but an IRL540 will run any size fan you want and will interface well with a µC. With regard to noise keep it's routing away from anything sensetive, traces carrying PWM'd power close together in pairs and twist any cables. You can of course get fans with built in controllers like say 4 wire PC caso fans, this takes the power control headache away and is what would be recomended on a pro design. anything bigger and you can look at ebmpapst fans that are grunty little speed controllable fans. |
| cdev:
It would be useful in a bench supply to have a record of peak current draw and /or if the current limit had been reached and activated, and maybe current x voltage x time. (watt hours or its equiv.) That way you would avoid the inevitable "why didn't you buy the meter on ebay" questions. The two line display you're using has the room for lots of additional info to be displayed beyond simply voltage and current. Since you likely dont have or need additional decimal places you could add additional functionality in the display. Even just a time display (clock) would be useful. A timer would also be very useful for some things. |
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