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News/Suggestions/Help / Re: Buy Aell Wanted section, compulsory country
« Last post by thm_w on Today at 09:18:55 pm »Would be nice, don't think its easily possible.
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Altium Designer / Re: How do I edit lines in mechanical layer 1?
« Last post by thm_w on Today at 09:17:45 pm »Select Mechanical 1 layer, at the top Place -> Line then draw the line to connect them.
Then once its complete, ctrl-a to select all, Design -> Board shape -> Define from selected objects
You could also delete it all and draw it in DXF again and re-import it.
Using Mech1 or Keepout layer shouldn't really make any difference. Assuming board edge clearance rules are in place.
Then once its complete, ctrl-a to select all, Design -> Board shape -> Define from selected objects
You could also delete it all and draw it in DXF again and re-import it.
Using Mech1 or Keepout layer shouldn't really make any difference. Assuming board edge clearance rules are in place.
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Projects, Designs, and Technical Stuff / Re: Design AC-DC power supply using Innoswitch and custom transformer
« Last post by xvr on Today at 09:14:07 pm »Quote
however will this circuit yeild any dangerous issue like shorting?I see no danger. It should work.
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Test Equipment / Re: Siglent SDS3000X HD and upgraded SDS1000X HD
« Last post by Martin72 on Today at 09:08:52 pm »Have you regretted getting a SDS800X HD as a stopgap/filler until your SDS3034X HD arrived ?
Not for a second, Rob.
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Projects, Designs, and Technical Stuff / Re: MCP3551 - May have misunderstood operation.
« Last post by SpottedDick on Today at 09:06:48 pm »Ah, OK! That was a perfect explanation! Vref is the centre voltage.
I get it now, thank you!
EDIT: I also had an OP-amp before this giving a small amount of gain to amplify the signal, I'm thinking this is just adding noise and will probably bring it out of the equation entirely.
I get it now, thank you!
EDIT: I also had an OP-amp before this giving a small amount of gain to amplify the signal, I'm thinking this is just adding noise and will probably bring it out of the equation entirely.
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Buy/Sell/Wanted / Re: Philips (Photonis) XX1080 50mm Image Intensifier with PSU
« Last post by ZGoode on Today at 09:05:16 pm »These look really neat. Definitely some cool engineering there. What am I looking at? Is it some kind of lens of sorts?
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Projects, Designs, and Technical Stuff / Re: MCP3551 - May have misunderstood operation.
« Last post by SiliconWizard on Today at 09:04:32 pm »So, you did get the differential input about right, but not the role of Vref.
The ADC will convert the *differential input* in the -Vref / +Vref range. If you use a Vref of 3V, then your differential range is effectively +/-3V, which is not what you want.
With a Vin- at 2V and the expected input signal on Vin+ between 2V and 3V, your differential input is in the 0V / 1V range. You'll need a Vref of 1V to get the full positive scale for 3V input.
And yes, you'll still lose the negative half in this case, so 1 bit of resolution.
If you want to get the full ADC resolution, you'll have to approach it like this:
- Put a reference voltage of 2.5V at Vin- (instead of 2V).
- Use a 0.5V reference voltage for Vref. (Vref accepts from 0.1V to VDD, so no problem there.)
You'll get the full 22 bits, obviously "centered" around 2.5V, but that doesn't matter, you'll just use the numeric output appropriately. You'll have negative values for inputs in the 2V to 2.5V range, and positive from 2.5V to 3V.
The ADC will convert the *differential input* in the -Vref / +Vref range. If you use a Vref of 3V, then your differential range is effectively +/-3V, which is not what you want.
With a Vin- at 2V and the expected input signal on Vin+ between 2V and 3V, your differential input is in the 0V / 1V range. You'll need a Vref of 1V to get the full positive scale for 3V input.
And yes, you'll still lose the negative half in this case, so 1 bit of resolution.
If you want to get the full ADC resolution, you'll have to approach it like this:
- Put a reference voltage of 2.5V at Vin- (instead of 2V).
- Use a 0.5V reference voltage for Vref. (Vref accepts from 0.1V to VDD, so no problem there.)
You'll get the full 22 bits, obviously "centered" around 2.5V, but that doesn't matter, you'll just use the numeric output appropriately. You'll have negative values for inputs in the 2V to 2.5V range, and positive from 2.5V to 3V.
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Projects, Designs, and Technical Stuff / Re: DIY 115V AC 400Hz Power source
« Last post by BrianHG on Today at 09:02:41 pm »Find a car amp or home audio amp which can do a true 2000 watt into 8 ohm and it will have enough voltage headroom to deliver 120v ac, up to 2000 watts.
Note that some home or pro stereo 500 watts/channel amps (for 8 ohm speakers) run in 'bridged' mono mode will also deliver 120v ac directly at speaker terminals up to 1000 watts max. (True 500watts RMS, not peak 500watts, otherwise you will need a 800watts peak per channel amp...)
However, remember you need to feed the left channel a true 400hz 1vrms while feeding the right channel an inverted version of the same 400hz unless your amp has a built in bridge function for 2x/4x the power output.
Also remember that there is no longer a true GND as one channel goes up 79v while the opposite channel goes down to -79v. The amp GND and chassis will be stuck in the center at 0v.
Note that some home or pro stereo 500 watts/channel amps (for 8 ohm speakers) run in 'bridged' mono mode will also deliver 120v ac directly at speaker terminals up to 1000 watts max. (True 500watts RMS, not peak 500watts, otherwise you will need a 800watts peak per channel amp...)
However, remember you need to feed the left channel a true 400hz 1vrms while feeding the right channel an inverted version of the same 400hz unless your amp has a built in bridge function for 2x/4x the power output.
Also remember that there is no longer a true GND as one channel goes up 79v while the opposite channel goes down to -79v. The amp GND and chassis will be stuck in the center at 0v.
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Projects, Designs, and Technical Stuff / Re: Design AC-DC power supply using Innoswitch and custom transformer
« Last post by VEGETA on Today at 08:58:32 pm »This switch include discharge resistor on each output channel that turned on when channel disabled (as followed from schematic in datasheet). You short output from both channels, so one of discharge resistor always will be connected parallel to output. Its value is 220-300 Ohm. You can use this switch if you can tolerate such surplus load.
worst case is 5v for 300 ohms = 16.7 mA. very tiny, won't make an effect.
however will this circuit yeild any dangerous issue like shorting?
a simpler solution is to use such a switch like this one: https://www.lcsc.com/product-detail/Toggle-Switches_YUEN-FUNG-ST-0-103-A01-T000-RS_C1788488.html
i want one which does not have luggs and stuff, but overall it is more expensive though, cheapest ever is a jumper but it is not elegant
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Repair / Re: E4433B RF sig gen repair
« Last post by microbug on Today at 08:58:00 pm »I tried bypassing the mixer chip with a 10dB pad. Instrument output looks exactly the same -- 2.7GHz signal. I also tried running it with the shield on the output board (mixer chip not bypassed), and it shifted to 1.1GHz (but still no sign of the signal it should be putting out).
I think I might have had a faulty connection in the measurements labelled 2 in the last post. That would suggest that there might be a dead component somewhere later in the RF signal path. If the desired signal isn't getting through, and there's a lot of 2.7GHz around, then I suppose the input to the next stage might just be coupled 2.7GHz, leading to that appearing at the final RF output.
I'll do some more probing around this weekend. I'm starting to get a bit fed up with this. The number of parts to check is quite small though -- since the problem is there for the whole instrument output range, it must be a part of the RF chain that is shared. That leaves just a few amplifiers and some PIN diodes to check. If I don't make some progress soon I will consider selling the unit for someone else to have a look at.
I think I might have had a faulty connection in the measurements labelled 2 in the last post. That would suggest that there might be a dead component somewhere later in the RF signal path. If the desired signal isn't getting through, and there's a lot of 2.7GHz around, then I suppose the input to the next stage might just be coupled 2.7GHz, leading to that appearing at the final RF output.
I'll do some more probing around this weekend. I'm starting to get a bit fed up with this. The number of parts to check is quite small though -- since the problem is there for the whole instrument output range, it must be a part of the RF chain that is shared. That leaves just a few amplifiers and some PIN diodes to check. If I don't make some progress soon I will consider selling the unit for someone else to have a look at.