| Products > Test Equipment |
| finding short on motherboards with a shorty (with display) |
| << < (33/37) > >> |
| kripton2035:
why not, but for me not a drawer component I have around, easier to get 2 ex of some basic silicon diode ? |
| Kean:
--- Quote from: wacd on March 13, 2024, 04:35:54 pm ---How abour this CMJA5050 https://my.centralsemi.com/datasheets/CMJA5050.PDF --- End quote --- Did you review the datasheet for that part? It has a 10% tolerance, takes over 10 seconds to come into regulation, and has a TC of -0.3mA/degC. It is not a precision part, and it also seems to need a supply of 8V or so to regulate. |
| wacd:
Okay, how do i limit the current to 50mA then? These are the results when i use the lab psu limited at 0.05A its almost perfect. |
| Kean:
--- Quote from: wacd on March 14, 2024, 05:38:22 am ---Okay, how do i limit the current to 50mA then? These are the results when i use the lab psu limited at 0.05A its almost perfect. --- End quote --- If you want precision, I would suggest changing the design to use an opamp controlled current source. https://en.wikipedia.org/wiki/Current_source#Op-amp_current_sources So, looking at the original Shorty schematic, R3 would be the sense resistor and selected for higher precision, and R1 would be replaced with a transistor controlled by the opamp. R2 and the DUT become the load. Assuming R3 stays at 1 ohm, you would need a voltage reference (the 5V or 3.3V rail may be OK) and divider to get the 50mV reference. Opamp would have to be selected for a low offset voltage. |
| wacd:
Thank you for providing information. I'll go and spend some time on this to learn it better so i can implement it , hopefully :) |
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