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ain_4 [2016/08/10 16:27] – [Power] latigid_onain_4 [2016/08/18 09:36] (current) – [Standalone use] latigid_on
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 ====== AIN_4 module ====== ====== AIN_4 module ======
  
-This is a simple way of scaling CVs (as might come from a modular) ready for an STM322F4 Core module. +This is a simple way of scaling CVs (as might come from a modular) ready for an STM32F4 Core module. 
  
 ===== Schematic ===== ===== Schematic =====
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 The circuit is a very simple series of two inverting amplifiers per channel. The first is a TL072 powered from +12/-12V, while the second is an MCP6002 powered from 3v3/0V (ground). It's possible to preset the ranges (see below) but it's probably more useful to use the associated [[Control Board]]. The circuit is a very simple series of two inverting amplifiers per channel. The first is a TL072 powered from +12/-12V, while the second is an MCP6002 powered from 3v3/0V (ground). It's possible to preset the ranges (see below) but it's probably more useful to use the associated [[Control Board]].
  
-For bipolar operation, a +5V reference may be switched in. The output of the first stage is interrupted by a pot in order to attenuate the signal. The second stage has variable gain from -1 to -0.5 by way of a switched resistor. Hence one can easily select between 0-5V, 0-10V and +/- 5V input ranges to optimise the signal amplitude reaching the ADC. Because the second op amp is powered at the same voltage as the MCU (ideally the same rail), its inputs are protected from over- and under-voltages.+For bipolar operation, a +5V reference may be switched in. The output of the first stage is interrupted by a pot in order to attenuate the signal. The second stage has switchable gain from -1 to -0.5 by way of a resistor. Hence one can easily select between 0-5V, 0-10V and +/- 5V input ranges to optimise the signal amplitude reaching the ADC. Because the second op amp is powered at the same voltage as the MCU (ideally the same rail), its inputs are protected from over- and under-voltages. 
 + 
 +Note the gain calculation, and beware the top of the signal may clip (harmlessly) if around 3.0V peak is exceeded on the second op amp stage.
 ---- ----
  
  
-===== BOM =====+===== BOM v1.2 =====
  
 ^Type     ^Qty ^Value ^Package ^Parts^Notes^ ^Type     ^Qty ^Value ^Package ^Parts^Notes^
 ^resistors^  ^resistors^
-|         |20   |49k9   |0204/7|R1, R2, R4, R5, R6, R7, R8, R10, R11, R12, R13, R14, R16, R17, R18, R19, R20, R22, R23, R24| +|         |20   |49k9 1% or better   |0204/7|R1, R2, R4, R5, R6, R7, R8, R10, R11, R12, R13, R14, R16, R17, R18, R19, R20, R22, R23, R24|49k9/30k resistors aren't so common. For almost equivalent behaviour, one could substitute e.g. 56k/33k. It's best to match pairs/threes or go for 0.1% tolerance parts| 
-|         |4    |30k    |0204/7|R3, R9, R15, R21|nominal gain can be adjusted e.g. (22k/49.9k)*5V = 2.2V| +|         |4    |30k 1%   |0204/7|R3, R9, R15, R21|nominal gain can be adjusted e.g. (22k/49.9k)*5V = 2.2V|
 ^capacitors^  ^capacitors^
-| |4|10p|025X050|C1, C3, C5, C7|+| |4|10p|025X050|C1, C3, C5, C7|20% (?)
 | |9|100n|025X050|C10, C12, C13, C14, C15, C16, C17, C18, C20|remove 1 if powering from Core| | |9|100n|025X050|C10, C12, C13, C14, C15, C16, C17, C18, C20|remove 1 if powering from Core|
 | |3|10u|electrolytic 2,5-6|C9, C11, C19|remove 1 if powering from Core| | |3|10u|electrolytic 2,5-6|C9, C11, C19|remove 1 if powering from Core|
 | |4|optional|025X050|C2, C4, C6, C8|can use another e.g. 10pF cap here for more filtering|  | |4|optional|025X050|C2, C4, C6, C8|can use another e.g. 10pF cap here for more filtering|
 ^inductors^  ^inductors^
-| |2|BEAD|5MM|L1, L2| +| |2|BEAD|5MM|L1, L2|or replace with wire link|
 ^ICs^  ^ICs^
 | |2|MCP6002P|DIL08|IC2, IC4|sockets are recommended| | |2|MCP6002P|DIL08|IC2, IC4|sockets are recommended|
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 +
 +===== Versions =====
 +
 +v1.2: first release.
  
 ===== Assembly ===== ===== Assembly =====
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   * four 10p as marked in pink   * four 10p as marked in pink
   * electrolytics in yellow   * electrolytics in yellow
-  * blue are optional+  * blue are optional (i.e. probably unnecessary)
   * remainder are 100n.   * remainder are 100n.
 {{:ain_4_10pf.png?nolink&300|}} {{:ain_4_10pf.png?nolink&300|}}
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 {{:ain_4_power_rails.png?nolink&300|}} {{:ain_4_power_rails.png?nolink&300|}}
 +
 +==== Headers ====
 +
 +For connection to a [[Control Board]], use pin headers placed on the opposite side as the rest of the components i.e. follow the silkscreen markings. It's convenient to use an **unsoldered** Control Board to align all of the pins at once.\\
 +
 +For standalone use, you probably want header pins (or sockets, or even bare wires if you wish) on the same side as the remaining circuitry.
 +
 ---- ----
  
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 ==== Standalone use ==== ==== Standalone use ====
  
-For simplest results, use the complementary [[Control Board]]. Otherwise see below for header functions.+For simplest results, use the complementary [[Control Board]]. Otherwise see below for header functions (viewed from the component side).
  
  
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   * with a 100k pot facing you, solder the left leg to 0V(ground)   * with a 100k pot facing you, solder the left leg to 0V(ground)
 +  * with the pot turned anticlockwise, the TL072 output is shorted to ground. While shorts are permitted in the datasheet, it's advisable to connect a small value resistor (e.g. 10-100R) between the left leg and ground.
   * centre to WIPER   * centre to WIPER
   * right to LEG   * right to LEG
ain_4.1470846422.txt.gz · Last modified: 2016/08/10 16:27 by latigid_on