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hesc_1314511
Level 3
Level 3
10 sign-ins First solution authored 10 replies posted
hallo , I am testing CY8CKIT-050B dev kit, can I use it to logger 24 input analog ? these are 24 analog accelerometrers , ouput fo zero X Y, Z is 900 mV , the value is between 700mV and 1.25V , Adc will be 20 bits or 24 bits , ADC inside are 3 multipelxed? can an instant measurement? thanks John
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If 16-bit is sufficient for your project, then existing DelSig-ADC can potentially handle the load.

8 inputs x 150Hz  = 1200Hz. The DS-ADC has 10kHz sampling rate limit in this mode, which is enough. It is unlikely that one can reach even this 16-bit limit using long wires from ADXL354 to PSoC5.

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odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

What sampling rate each accelerometer needs? The DelSigADC can go only up to 20-bit, with aggregate sampling rate of 180Hz at this resolution.

What is accelerometer P/N?

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hesc_1314511
Level 3
Level 3
10 sign-ins First solution authored 10 replies posted

hz will be right , 

ADXL354 accelerometer

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Reading datasheets is invaluable. The ADXL354 is analog output X,Y,Z with output rates up to 1kHz. So, depending  on the expected agility of the system, PSoC5 (@20-bit) will be able to sample only one ADXL354 module at about 180Hz / 4 / 3 = 15Hz max. Here 180Hz is the max sampling rate a 20-bit resolution, divider 4 because of multiplexing X,Y,X, and each new sample has to be primed by 4 blank samples, and divider 3 is for X,Y,Z.

There is another part with digital output ADXL355, which has both SPI and I2C options, which is more appropriate for you goal  of 24 units. Judging from the price of ~$50 per unit, it is not a home project, so you have an option.

 Using ADXL355 with digital output is probably the only right choice, as having 24 units implies long connection wires, which is not suitable for 20-bit ADC sampling.

Secondary: 24 of ADXL355 will need either 24 SPI or 24 I2C ports, which  (I believe) is hard to impossible on the PSoC5. The SPI can be emulated in s/w, but there are other uC, which could do this more efficient. Overall suggestion is to start with one ADXL355 (digital interface) and look  for other uC targets.  

thank you for your evaluation, can you suggest me a suitable uC for my work? I have to use the analog ADXL354 accelerometer, so I have to do the conversion with the uC minimum 20 bit, and with 8 channels I have to have at least 150Hz for each channel, do you also have a uC with 8 single ADC channels?

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You have to be realistic with your goal. There are no such uC to sample 24 inputs at 20-bits at the rate of 150Hz each.

There are various AI front end from the Analog devices, which can be used as an interface between the ADXL354 and uC, but the cost and the effort required is out of the scope of the project. Besides, ADXL355 already incorporates such interface.

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it's 8 analogo channels in my data logger at now, this I need now

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If 16-bit is sufficient for your project, then existing DelSig-ADC can potentially handle the load.

8 inputs x 150Hz  = 1200Hz. The DS-ADC has 10kHz sampling rate limit in this mode, which is enough. It is unlikely that one can reach even this 16-bit limit using long wires from ADXL354 to PSoC5.

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From your experience, do you believe that the ADXL355 with its digital output, and the ADXL354, where I do the analog to digital conversion, let's assume 20 bit, have the same sensitivity and scale precision? consider that I need to have at least 350 points per degree of inclination on the X Y Z axes 

thanks

John

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1. According to the datasheet, the ADXL354 and ADXL355 have same nominal accuracy. ADXL355 has ADC build-in, eliminating all hassle of performing the sampling and filtering of the analog signal of the ADXL354. It has digital output, making it immune from the external analog noise.

2. I believe there is a misconception regarding ADXL354/355 functionality. These chips are ACCELEROMETERS, and do not provide angular measurement. They can only measure X,Y and Z linear acceleration, not angle.

There are another methods of measuring angles of rotation. To be able to assist you better, please describe your project in as much details as you can (like robotic arm or human limbs motion analysis, etc.)

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hesc_1314511
Level 3
Level 3
10 sign-ins First solution authored 10 replies posted

and how many input for accelerometers are?

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