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Re: HX711: VCC and VDD at 3.3V?

 by UhClem ¦  Sun Feb 03, 2019 7:08 am ¦  Forum: Load Cells & Amplifiers ¦  Topic: HX711: VCC and VDD at 3.3V? ¦  Replies: 4 ¦  Views: 178

So long as the voltage is greater than the drop out voltage of the HX711 analog supply regulator, it should work fine.

Re: OpenScale and Increased Report Rate

 by UhClem ¦  Wed Jan 30, 2019 4:50 pm ¦  Forum: Load Cells & Amplifiers ¦  Topic: OpenScale and Increased Report Rate ¦  Replies: 7 ¦  Views: 176

No. The jumper sets the conversion rate of the HX711 to either 10SPS or 80SPS. The rate at which results are reported depends on other things: how long of a delay between loop iterations and how many samples are averaged into one report. Delay long enough and you will miss samples. With a delay of 1...

Re: OpenScale and Increased Report Rate

 by UhClem ¦  Wed Jan 30, 2019 1:32 pm ¦  Forum: Load Cells & Amplifiers ¦  Topic: OpenScale and Increased Report Rate ¦  Replies: 7 ¦  Views: 176

The rate appears to be determined by "delay(1000)". Adjust as required. /************************* READ HX711 *********************************/ void readOpenScale() { Serial.print("Reading: "); Serial.print(scale.get_units(AVG_FACT), RESOLUTION); //scale.get_units() returns a float Serial.print(" g...

Re: OpenScale and Increased Report Rate

 by UhClem ¦  Wed Jan 30, 2019 10:08 am ¦  Forum: Load Cells & Amplifiers ¦  Topic: OpenScale and Increased Report Rate ¦  Replies: 7 ¦  Views: 176

The jumper changes the conversion time on the HX711 but nothing else. You will have to tell the firmware the new higher reporting rate for anything to change. The SparkFun code checks to make sure that the requested rate is compatible with the serial data rate and sensors so be sure to use something...

Re: Trouble with using LMV358 to bridge headset and teensy

 by UhClem ¦  Wed Oct 17, 2018 7:45 am ¦  Forum: SparkFun Product Questions ¦  Topic: Trouble with using LMV358 to bridge headset and teensy ¦  Replies: 3 ¦  Views: 225

It is difficult to tell from what I have found but it is possible that the mic requires a DC bias voltage to operate. The documents mention a resistor (2.2K) in series with a small voltage (2.2V) but it isn't clear if that is needed by the mic or just to detect switch closures.

Re: Hall Sensor Signal Conditioning

 by UhClem ¦  Thu Aug 30, 2018 11:06 am ¦  Forum: Projects ¦  Topic: Hall Sensor Signal Conditioning ¦  Replies: 9 ¦  Views: 348

The only problem with your circuit is the common mode range of the opamp. Try it out in Spice (LTSpice is what I use) if you don't believe me. You could fix that by increasing the opamp supply voltage except that your particular part can't take much more than 5V. (One minor complication is that the ...

Re: Hall Sensor Signal Conditioning

 by UhClem ¦  Wed Aug 29, 2018 4:26 pm ¦  Forum: Projects ¦  Topic: Hall Sensor Signal Conditioning ¦  Replies: 9 ¦  Views: 348

Analysis using the traditional concepts of the virtual open and the virtual short: Input current is next to nothing so the inputs to the opamp are open circuits. Feedback assures that V+ = V- just as if they were shorted together. But they aren't, see virtual open. Using the virtual short the curren...

Re: Hall Sensor Signal Conditioning

 by UhClem ¦  Wed Aug 29, 2018 1:15 pm ¦  Forum: Projects ¦  Topic: Hall Sensor Signal Conditioning ¦  Replies: 9 ¦  Views: 348

Is the solution to put a 10K in series with the '+' input? No. It is already working as expected. Or at least as well as can be expected so close to the limit of the common mode input voltage range. Try applying a test current and watch as the output voltage decreases. The 10K resistor would do not...

Re: Hall Sensor Signal Conditioning

 by UhClem ¦  Wed Aug 29, 2018 10:50 am ¦  Forum: Projects ¦  Topic: Hall Sensor Signal Conditioning ¦  Replies: 9 ¦  Views: 348

Did you notice the common mode input voltage range for that opamp? With a 5V supply 4V is at the edge of its range. But you have misunderstood the operation of the circuit. An opamp has a huge excess of open loop gain so with negative feedback like you have here, the output voltage will be driven so...

Re: Trouble with a Transducer - Trying to switch it off

 by UhClem ¦  Wed Jul 25, 2018 7:35 pm ¦  Forum: Projects ¦  Topic: Trouble with a Transducer - Trying to switch it off ¦  Replies: 10 ¦  Views: 784

That image is not nearly as useful as an actual schematic. For example, what is the sensor part number? I looked up the part number shown and that is a 5VDC part. The circuitry inside the sensor will not disconnect from its positive supply just because you removed its ground connection. So it could ...

Re: Rocket accelerometer

 by UhClem ¦  Fri Jun 15, 2018 1:35 pm ¦  Forum: Projects ¦  Topic: Rocket accelerometer ¦  Replies: 13 ¦  Views: 863

i need to collect the acceleration's DATAs as well, so i must use three axis. the kalman filter will help to detect apogee ( the sensor detect the burnout ) so why would it be wasted? The extra two axis will pick up vibration and not much else. So unless you are trying to measure that, it is a wast...

Re: Rocket accelerometer

 by UhClem ¦  Thu Jun 07, 2018 7:40 pm ¦  Forum: Projects ¦  Topic: Rocket accelerometer ¦  Replies: 13 ¦  Views: 863

I think you would want both, to more accurately measure the two acceleration regimes. If you use one then scale factor (slope) errors do not matter since you start at zero velocity and end at zero. But if you use one accel under thrust and a different accel near apoge, their scale factor errors mat...

Re: Rocket accelerometer

 by UhClem ¦  Thu Jun 07, 2018 6:41 pm ¦  Forum: Projects ¦  Topic: Rocket accelerometer ¦  Replies: 13 ¦  Views: 863

@UhClem: Don't you agree that for apogee detection, one would want to use a +/- 2g (or similar) accelerometer? Absolutely not. What you are doing is integrating the acceleration and waiting for the velocity to go from positive to negative. I still have a BlackSky AltAcc2 which uses an ADXL50 accel ...

Re: Rocket accelerometer

 by UhClem ¦  Thu Jun 07, 2018 10:20 am ¦  Forum: Projects ¦  Topic: Rocket accelerometer ¦  Replies: 13 ¦  Views: 863

If the only purpose is determining apogee, then one axis is all you need.

If the only sensor is the accel then the Kalman filter is wasted.

Re: MPU9250 schematics

 by UhClem ¦  Wed Sep 27, 2017 8:46 am ¦  Forum: Projects ¦  Topic: MPU9250 schematics ¦  Replies: 1 ¦  Views: 335

falaroce wrote:Our CS# pin is connected directly to VCC, Does the lack of a pullup resistor could be the problem?
No. See Figure 2 in the MPU-9250 data sheet.

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