This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
university:tools:m1k:analog-mux [19 Aug 2016 20:17] – add 74HC4051 based bob Doug Mercer | university:tools:m1k:analog-mux [30 Dec 2020 17:17] – add sparkfun links Doug Mercer | ||
---|---|---|---|
Line 1: | Line 1: | ||
======Multichannel analog interface hardware for the ADALM1000====== | ======Multichannel analog interface hardware for the ADALM1000====== | ||
- | The two analog input channels of the ADALM1000 provide a high input impedance and wide dynamic range which is very helpful for many of the measurements that students would be making around their laboratory activities. However, there are only the two analog inputs. Often, there are many more than two signals in the circuit or system under investigation that you would like to monitor. Or there could be a number of low bandwidth sensors, such as ambient temperature or light levels around a room, that need to be measured or monitored over long durations of time when gathering experimental data. As a solution to this need, the following multi-channel analog multiplexer is proposed. | + | The two analog input channels of the ADALM1000 provide a high input impedance and wide dynamic range which is very helpful for many of the measurements that students would be making around their laboratory activities. However, there are only the two analog inputs. Often, there are many more than two signals in the circuit or system under investigation that you would like to monitor. Or there could be a number of low bandwidth sensors, such as ambient temperature or light levels around a room, that need to be measured or monitored over long duration times when gathering experimental data. As a solution to this need, the following multi-channel analog multiplexer is proposed. |
- | A first example | + | A first incarnation of this very simple design uses one CD4052 dual 4:1 analog multiplexer (or the equivalent 74HC4052/ |
- | {{ : | + | {{ : |
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | For ease of use the 6 pins on the digital connector (DIGITAL) pass through to the second digital connector (DIGITAL2). Similarly the 6/8 pins of the ANALOG connector pass through to one row of the 2X8 pin second | + | {{ : |
- | Digital outputs PIO 0 and 1 are used to address the four mux channels. Digital output PIO 2 drives the INH inhibit input of the mux which turns off all the switches. | + | <WRAP centeralign> |
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | For ease of use 6/8 pins of the ANALOG connector pass through to the second 1X8 pin analog connector (ANALOG2). The 8 analog inputs of the mux fill out the other 8 pin MUXIN connector. The X and Y outputs of the mux can be connected to input only AIN/BIN pins through solder jumpers. | ||
+ | |||
+ | Digital outputs PIO 0 and 1 are used to address the four Mux channels. Digital output PIO 2 drives the INH inhibit input of the Mux which turns off all the switches. | ||
The multiplexer is powered from the fixed + 5V supply on the ALM1000 analog connector which will limit the allowed range of analog input voltages to be within the same 0 to + 5V supported by the analog inputs. The 6/8 analog connector pins of the ALM1000 including the +5 volt and +2.5 volt power supplies are included in the female connector on the right and can be used to power sensor electronics, | The multiplexer is powered from the fixed + 5V supply on the ALM1000 analog connector which will limit the allowed range of analog input voltages to be within the same 0 to + 5V supported by the analog inputs. The 6/8 analog connector pins of the ALM1000 including the +5 volt and +2.5 volt power supplies are included in the female connector on the right and can be used to power sensor electronics, | ||
- | Figure 2 is a rendering of what the top of the PCB will look like. Design files for all the example board layouts are included in the zip file linked to at the end of this document. | + | {{ : |
- | {{ : | + | <WRAP centeralign> |
- | <WRAP centeralign> | + | There are many use cases that can benefit from more than two scope inputs. Below in figures 6 and 7 are examples showing the Mux being used to view multiple outputs of a poly-phase filter. |
- | Here is another smaller incarnation of the analog multiplexer in figure 3, with the multiplexed connections on a separate single row female header rather than putting everything on the 2X8 header. This one stacks well with the two ALM1000 breadboard adapters proposed in this document. | + | {{ : |
- | {{ : | + | <WRAP centeralign> |
- | <WRAP centeralign> | + | Another use case is the artificial lumped LC transmission line [[https:// |
- | In figure 4 we have a modified version of the protoboard/ | + | {{ : |
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | The simplest way to use the 74HC4052 is just on a small bit of proto-board with male jumper wires attached as show in figure | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | There are other analog multiplexer configurations in the generic CD4XXX series of CMOS ICs. The CD4051 is a single 8:1 mux and the CD4067 is a single 16:1 mux. The old Motorola MC14529B analog selector can be a configured as a dual 4-channel or single 8-channel device depending on how the input controls are used. By using 3 or all 4 of the digital PIO bits and two of these single multiplexers either 16 or even 32 signal channels could be measured. This [[https:// | ||
+ | |||
+ | The SparkFun analog mux boards do not come with header connectors so they would need to be added. The pins on the connector do not line up with the M1k connectors so male to male jumpers would be needed as shown in the figure 9. | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | In figure 10 we have a modified version of the protoboard/ | ||
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | There are other analog multiplexer configurations in the generic CD4XXX series of CMOS ICs. The CD4051 is a single 8:1 mux and the CD4067 is a single 16:1 mux. The old Motorola MC14529B analog selector can be a configured as a dual 4-channel or single 8-channel device depending on how the input controls are used. By using 3 or all 4 of the digital PIO bits and two of these single multiplexers either 16 or even 32 signal channels could be measured. These two mux breakout boards are available from SparkFun, the [[https:// | + | There are other analog multiplexer configurations in the generic CD4XXX series of CMOS ICs. The CD4051 is a single 8:1 mux and the CD4067 is a single 16:1 mux. The old Motorola MC14529B analog selector can be a configured as a dual 4-channel or single 8-channel device depending on how the input controls are used. By using 3 or all 4 of the digital PIO bits and two of these single multiplexers either 16 or even 32 signal channels could be measured. These two mux breakout boards are available from SparkFun, the [[https:// |
Another functionally similar option is the [[http:// | Another functionally similar option is the [[http:// | ||
Line 41: | Line 67: | ||
The TTL compatible digital input minimum logic high voltage spec for the ADG609 is 2.45 V where the CD4052 and 74HC4052 minimum logic high voltage spec is 3.15V which is just slightly lower than the 3.3V typical logic high output voltage generated by the ALM1000. The actual logic threshold for the CD4052 is probably closer to VDD/2 ( 2.5V ) at room temperature and seems to work ( given this will probably be used at room temperature ) but there could be little margin in certain cases. The TTL compatible 74HCT4052 has a 1.6 volt typical logic high threshold which is perfect for the 3.3 V CMOS outputs of the ALM1000. | The TTL compatible digital input minimum logic high voltage spec for the ADG609 is 2.45 V where the CD4052 and 74HC4052 minimum logic high voltage spec is 3.15V which is just slightly lower than the 3.3V typical logic high output voltage generated by the ALM1000. The actual logic threshold for the CD4052 is probably closer to VDD/2 ( 2.5V ) at room temperature and seems to work ( given this will probably be used at room temperature ) but there could be little margin in certain cases. The TTL compatible 74HCT4052 has a 1.6 volt typical logic high threshold which is perfect for the 3.3 V CMOS outputs of the ALM1000. | ||
- | This analog multiplexer data acquisition add-on board is a perfect candidate for writing a custom program using the ALM1000 Python interface software package ([[https:// | + | This analog multiplexer data acquisition add-on board is a perfect candidate for writing a custom program using the ALM1000 Python interface software package ([[https:// |
{{ : | {{ : | ||
- | <WRAP centeralign> | + | <WRAP centeralign> |
- | + | ||
- | A modified version of the [[university: | + | |
- | {{ :university: | + | The [[university: |
- | <WRAP centeralign> | + | {{ : |
- | In this example a CD4024 binary counter is driven by a 0 to 5 V square wave output from channel A. The divide by 2, 4, 8 and 16 outputs of the counter drive a 4 bit resistor DAC using an AD8541 rail to rail CMOS opamp as an inverting summing amplifier. The top green trace is the output square wave from channel | + | <WRAP centeralign> |
- | One important feature of the program is that a sync or sweep start pulse is output on the PIO 3 digital output pin just before each analog sweep starts. This pulse is used to reset the CD4024 digital counter to the same starting condition for each sweep. Using this " | + | One important feature of the program is that a sync or sweep start pulse is output on the PIO 3 digital output pin just before each analog sweep starts. Using this " |
- | + | ||
- | The program has much of the same functionality as the full [[university: | + | |
| | ||