Transmission line emulation.

Started by Clive Arthur in sci.electronics.design18 hours ago 21 replies

I wanted to make a physical device to emulate a long transmission line. This particular line has lots of C, I know the R and can guestimate the...

I wanted to make a physical device to emulate a long transmission line. This particular line has lots of C, I know the R and can guestimate the L. So I built a lumped line using T sections, 10 Rs, 10 Ls and 9 Cs to ground. So far so standard. It didn't perform very well, and I think part of the reason was the impedance being too large - dominated by the first R - so limiting the pow...


how to optimize for multistage gain selection

Started by Anonymous in sci.electronics.design1 day ago 31 replies

I'm trying to design a two stage amplifier for a sensor readout and I would like those stages to be configurable, but I also need to have the...

I'm trying to design a two stage amplifier for a sensor readout and I would like those stages to be configurable, but I also need to have the overall gain vs. configuration curve to be such that every new step is ~5% increase w.r.t. the previous. So let's say I have 3 control bits on the first amplifier and 4 for the second, how would I design the set of values those gains need to be at? Is the...


Spurious triggering of 4013 flip-flop

Started by Terry Pinnell in sci.electronics.design2 days ago 70 replies

One of my garden lamp circuits is shown here: https://www.dropbox.com/s/10cc6lwfrsqjp68/DiningLamp-Post.jpg?raw=1 But the CMOS 4013...

One of my garden lamp circuits is shown here: https://www.dropbox.com/s/10cc6lwfrsqjp68/DiningLamp-Post.jpg?raw=1 But the CMOS 4013 flip-flop circuit suffers from occasional spurious triggering. Somehow it frequently gets activated overnight. Frustratingly I?m unable to pin it down. But I suspect it may be due to the very long wire (60 ft or so) carrying the high-going brief input signal...


favorite I2C temp + humidity sensor

Started by Winfield Hill in sci.electronics.design2 days ago 15 replies

Seeking comments about your favorite I2C digital temperature plus humidity sensor. We've been using Bosch BME280, which combines...

Seeking comments about your favorite I2C digital temperature plus humidity sensor. We've been using Bosch BME280, which combines Press+Temp+Humidity, but want T+H only. Now thinking of IDT's HS3001 Digital Relative Humidity and Temperature Sensor, which is also I2C. Honeywell offers T+H sensors that include a hydrophobic condensation-resistant filter, e.g., HIH7131-021-001. ...


testing an ADC

Started by John Larkin in sci.electronics.design2 days ago 8 replies

We have a product with a 12-bit ADC that's being clocked around 60 MHz, with the data poured into an FPGA. We want to do a good production...

We have a product with a 12-bit ADC that's being clocked around 60 MHz, with the data poured into an FPGA. We want to do a good production test. We can route a big triangle wave into the adc and take a lot of samples. Our thinking is that each bit should be high about 50% of the time, and we can set limits on that. This will catch bits stuck high or low, bits shorted to other bits, ope...


Microplastics are raining down from the sky

Started by Anonymous in sci.electronics.design3 days ago 25 replies

Scientists discover large amounts of tiny plastic particles falling out of the air in a remote mountain...

Scientists discover large amounts of tiny plastic particles falling out of the air in a remote mountain location. https://www.nationalgeographic.com/environment/2019/04/microplastics-pollution-falls-from-air-ev en-mountains/


No shame to shim.

Started by George Herold in sci.electronics.design3 days ago 17 replies

So I've got these big coils. ~12" diam, ~150 turns per side*. Big coils here. https://www.teachspin.com/optical-pumping The homogeneity of...

So I've got these big coils. ~12" diam, ~150 turns per side*. Big coils here. https://www.teachspin.com/optical-pumping The homogeneity of these coils sets the high field signal linewidth (LW). LW*signal is ~constant. About 1/2 of the coils can have the LW improved by a little mechanical shimming of the three mechanical support points. (mostly the top one.) ~5-10% of them fail** ...


Climate change erosion feeding deep ocean trash dump

Started by Anonymous in sci.electronics.design3 days ago 7 replies

There are growing concerns that increasing coastal and river-bank erosion is carrying millions of tonnes of long-buried rubbish into deep ocean...

There are growing concerns that increasing coastal and river-bank erosion is carrying millions of tonnes of long-buried rubbish into deep ocean canyons, where toxic waste and plastics will remain for decades. This is the beginning of the end, troubles reinforcing troubles. https://www.aljazeera.com/news/2019/04/climate-change-erosion-feeding-deep-ocean-trash-dump-1904 15112233494.html


Charger

Started by C_Mechanic in sci.electronics.design3 days ago 3 replies

Hi All, I would like to build a nice general purpose Li-ion/gel charger for 1.5V batteries/cells thru 12V auto gels. Is there a SoC that will...

Hi All, I would like to build a nice general purpose Li-ion/gel charger for 1.5V batteries/cells thru 12V auto gels. Is there a SoC that will do this? Monitoring of overheating and/or overcharging a must have! :-) .- Keep the faith, --------------------------------------------------. | | | Ben aka cMech Web: htt...


digital I/Q

Started by John Larkin in sci.electronics.design3 days ago 17 replies

I want to measure the phase angle between two 100 MHz waveforms. One way to do that is to phase shift one of them 90 degrees and mix...

I want to measure the phase angle between two 100 MHz waveforms. One way to do that is to phase shift one of them 90 degrees and mix those two with the other, and lowpass the I and Q products. The filtered I and Q voltages plot a circle as a function of the phase difference, and the angle is the arctan of those two voltages. If I do all that inside an FPGA (except the analog filters) I'...


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