Products > Test Equipment
Scope Current Probe Deskew Fixture PCB Project
tautech:
--- Quote from: steve1515 on August 20, 2020, 02:12:10 am ---I've updated my schematic to simplify it a little bit and also have a 3D render of my board. What do you guys think?
--- End quote ---
I'd suggest additional USB footprints for the 5V supply.
Plain old USB-B as most of us have plain A-B cables lying around that came with our instruments.
Kean:
An alternate power connection seems like a good idea. Micro USB is convenient I guess, but I also like having a convenient way to power things off a lab supply.
I see you changed from 2 x 10R 2W resistors in series, to a single 20R 2W resistor. What footprint is that? It looks huge compared to the DPAK, so guessing 4527? A bit harder to source?
Jay_Diddy_B:
Hi,
Assuming 50% duty-cycle.
Dissipation in R4
0.5 x 2.5 x 2.5 / 20 = 0.156W (no need for a 2W resistor)
Dissipation in R3 = 0.5 x (2.52 + 52) /20
= 0.78W
I would use 5 x 100 \$\Omega\$ 1206 in parallel.
+1 on alternative to the USB for power (too fragile) add alternative in parallel.
Regards,
Jay_Diddy_B
tautech:
The resistors in what we are copying this from, the Siglent deskew fixture do get warm but not very warm.
This is the unit in this pic however as it's nearly 5MB ::) I'll only link the post here:
https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg3142106/#msg3142106
Later a few posts down is Martin's RE diagrams.
Jay_Diddy_B:
Hi,
I have looked carefully at the high resolution picture that was posted by forum member Martin72. This is what I see from the photo:
I have not drawn the cmos 555 circuits.
I have indicated the power dissipations in the resistors.
I have shown correctly the relationship between the coil, the resistors and the voltage test points.
By connecting the voltage test point to the bottom resistor, this guarantees that the voltage and current are in phase.
Regards,
Jay_Diddy_B
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