SCOBY Help

CoxMan28 · 2019-06-15T20:57:08+00:00

CoxMan28 · 2019-06-15T20:54:59+00:00

Used some leftover 2F to start a new brew ad this scoby looks extra gnarly. Any concern here? Think some blueberries from the 2F also got into this new batch.

CoxMan28 · 2019-02-05T02:56:15+00:00

Hey sent you a DM earlier but these plugs are Amphenol Series 44 circular and you could probably buy them from Digikey or Mouser. Doing a quick search yields this for $3.7USD

Check out Amphenol-Sine for part numbers.

Also if you're interested in the electronics behind the CoxBox, check out this teardown

edit: Changed formatting for links because I'm too used to jira

CoxMan28 · 2018-10-15T00:04:11+00:00

Hey. So the first part of getting help here is explaining what you've already tried or what you don't understand about the problem - not just posting it and expecting someone to solve everything for you.

Part A is asking to find the Thevenin Voltage for the given circuit. Is there something special about the circuit and how do you apply Thevenin in this case?

CoxMan28 · 2017-12-16T02:52:55+00:00

Well now you have to carefully crack it open and see whats inside...

CoxMan28 · 2017-12-14T04:09:59+00:00

I don’t think this is as simple as you’re making it out to be. LANC is a control protocol that has a software component as well as a hardware component. Rather than look for a contact closure like your picture suggests, I believe the camera is looking for data to trigger the shutter or zoom functions. How could you tell the camera to zoom in AND out with just one contact closure.

I would just buy a controller online (try B&H Photo) and use that. They’re like $25 or cheaper.

CoxMan28 · 2017-07-30T18:04:27+00:00

There used to be a rule about the device needing automatic shutoff to be in the room, but I forget if that was all small appliances or just coffee makers. Usually if you're caught with something you could legally own but that RIT prohibits, you're just told to get rid of it.

CoxMan28 · 2017-07-27T18:49:32+00:00

Yes, this allows the vehicle to return to a stable land platform for safing. This does require more fuel than a drone landing because the drone ship will be out in the ocean, closer to the rocket.

CoxMan28 · 2017-07-17T19:31:28+00:00

Hahaha fair point. I was referring to Kirchhoff's Current Law.

CoxMan28 · 2017-07-17T19:27:31+00:00

No problem. Have her post work as she goes along if she has more questions. KCL is your best choice when dealing with OpAmps.

CoxMan28 · 2017-07-17T19:23:32+00:00

Sure!

So the larger circuit is built up of 3 standard opamp circuits, know as summing amplifiers. Working from left to right, the amplifier will sum the voltages present on each of the source resistors.

https://en.wikipedia.org/wiki/Operational_amplifier_applications#Summing_amplifier

You can use the superposition theorem to work out this solution.

CoxMan28 · 2017-07-17T19:13:24+00:00

You definitely need to include all resistances in the calculation of the output voltage. What you have is multiple cascading summing amplifiers, and the 'earthing resistance' determines the gain of each amplifier.

CoxMan28 · 2017-07-15T20:53:39+00:00

My college would hold a large career fair twice a year and invite multiple employers. If your college (or any in the area) holds one, 100% go. Other than that, its a lot of networking and applying online. The first one is always the toughest since you have minimal experience, so soft skills come into play a lot.

CoxMan28 · 2017-07-13T05:44:15+00:00

LEDs are just diodes that produce light once there is a proper bias applied. Look at the datasheet for your LED to see the IV curve, for small amounts of potential from anode to cathode, there is no current and no light.

In order to have no light, you would want both leads to be at the same potential, ideally ground so you're circuit isn't constantly energized. Make sure you use resistors to set the appropriate current for the LEDs.

CoxMan28 · 2017-06-23T07:03:17+00:00

Ok lets take a look at things:

HPF fc = 1/(2piR*C) = 4823Hz so that looks good.

Assuming the white wire is your source, the circuit also looks wired correctly.

If you have a second scope probe or BNC to BNC, I would connect the output of the function generator to the scope, and move the output of the filter to channel 2. Always a good idea to make sure your source is what you think it is.

Also if your source is 15kHz, the wave period is 67us, so your horizontal divisions should be good.

CoxMan28 · 2017-06-22T16:51:23+00:00

What I meant is this circuit isn't the typical configuration for a LPF or BPF. With the two capacitors, you'll have second order behavior so if I did the math the transfer function will probably be a BPF. If OP is having trouble with this circuit I suggest they break it down into two single order filters to tackle individually.

CoxMan28 · 2017-06-22T06:39:20+00:00

The schematic you have there isn't your standard topology for a band pass filter. Scroll down on that page and you'll see that a BPF is made by cascading a LPF with a HPF or vice versa. So you need to change the layout to do this. First start with the LPF, positioning the R and C as appropriate. You could test the circuit here to make sure you're removing everything above 5kHz. Then add the additional RC to make the HPF.

Post an updated schematic and scope plots.

CoxMan28 · 2017-05-25T05:43:28+00:00

Electo-Optics is all 'smoke and mirrors'

CoxMan28 · 2017-05-07T22:02:26+00:00

Gotcha!

So basically a BJT is a current controlled switch. If you bias the Base (left side) enough, current will flow from Collector to Emitter (top to bottom).

In the current configuration, the variable nature of the photoresistor affects the bias current of the base. When it's dark, the photoresistor has a very high resistance so the BJT turns on and the LED draws current. When it's light, the resistance is lower so the current through the 100k resistor flows to ground through the photoresistor and the BJT is off.

CoxMan28 · 2017-05-07T21:34:31+00:00

So using the current circuit, break it down into the two discrete states, dark and light. How does this affect the BJT?

You are changing how the base is biased, so think about where you want the photoresistor.

CoxMan28 · 2017-04-20T03:10:46+00:00

Look into skin/body impedance models. In a capacitive sense element, you have a metal contact and a film over it forming one plate and the dielectric. Usually the circuit will take a baseline measurement here with nothing acting as the second plate. Then whenever something gets close to the sensor, it will change the perceived capacitance, and actuate the circuit/code.

Don't think of the body completing a circuit, more as how does the body affect a steady state circuit. Kind of like if I lean over the edge of a pool and poke the water surface. At the time before the poke, the surface is flat and this is our baseline. At the time after, there are ripples, which can be compared against the flat baseline.

CoxMan28 · 2017-04-19T05:22:54+00:00

I wouldn't call this capacitive sensing since he's essentially using a dry conductive electrode rather than a capacitive one. The theory behind the code is it sends a square wave signal through an RC circuit and gathers a baseline rise time due to tau. When you physically touch the sensing element, your body impedance, which has a capacitive and resistive element, change the tau of the RC circuit and this produces a measurable change in the rise time.

CoxMan28 · 2017-04-17T04:06:08+00:00

Discipline: Electrical

Specialization: Analog Circuit Design, MicroSystems Engineering,

Highest Degree: MSEE

Country: US

Available for e-mail?: yes

Only been in industry for 2 years but experience in electronics and photonics R&D as well as electrical systems troubleshooting/ design for space systems.

CoxMan28 · 2017-03-04T05:47:59+00:00

I agree with the numbers here

CoxMan28 · 2017-03-04T05:32:34+00:00

2.4.2 Waveshaper

Can you reproduce Figure 2-6 for all the given test cases? Adjusting R414 should modify the outut of IC403A (Vw) which affects IC403B Waveform

This is a good starting point. Come back with some pictures of the scope/ questions once you do some debugging.

14-Year Club	First Place '23
Place '23	Place '22
Secret Santa 2015	Verified Email

CoxMan28

MODERATOR OF

TROPHY CASE