IT: Computer Controlled Switch (CCS) (158.html)
Keywords: Raspberry, Pi, Pi Pico, CCS, Computer-Controlled-Switch, Computer, USB, LED
Introduction
The Computer Controlled Switch (CCS) has been designed to be inserted in any switched circuit in a building. Some examples of such switches are described in this article. The first example of a switched circuit (where the CCS could be inserted) is a 5v DC Doorbell circuit. (Some doorbell chimes use 12 volts AC, which is a different case.) A second example of a switched circuit (where the CCS could be used) is a 5V DC thermostat that controls a fireplace. A third example is the use of a "solenoid" to turn on-and-off a loud-speaker. Brief descriptions of the second and third applications follow. Then the doorbell application will be described in vivid detail.
Application Case II: 5v DC Thermostat
A thermostat is a special type of switch that is automatically switched On when the temperature is too low. When the thermostat turns On, the heater (e.g. a nearby fireplace) begins to warm up the area. As the area warms up, the thermometer in the thermostat reacts to the increasing temperature. When the temperature is high enough, the thermostat turns Off. This turns off the fireplace. Often there is a manual switch that can be used to turn on/off the fireplace. A CCS can be used to remotely control the fireplace. Instead of using the manual switch, a computer can command the CCS to turn on/off the fireplace.
Application Case III: Controlling the volume of an electronic speaker in a home office.
The author apologises in advance for contriving this application. Consider the situation where a speaker has been installed in room which is now a "home office".This speaker and other speakers play music throughout the whole house from a central music system. The person works at a desk in the middle of the room that is the "home office". The person wishes to turn off this speaker when talking on the phone. Some kind of switch is needed to do this, but the installation of a simple "speaker switch" at the desk would require the installation of unsightly audio wires running across the floor. A Raspberry Pi computer already exists in an adjacent room near the wires driving the speaker. A CCS can be connected to a USB port on the Raspberry. One solution is to buy an inexpensive SSR40 solenoid (Source 04) that is described below under the heading "AC/DC Solenoids From the Orient". One wire of the pair of speaker wires can be connected to pass through the solenoid. The solenoid can be connected to the CCS which is connected to the Raspberry Pi computer via the USB cable. Finally the computer on the desk in the home office can use existing Remote Desktop Connection (RDC) software via the home router to wirelessly control the Raspberry Pi. A "diagram" is shown below:
Computer
running wireless wireless Raspberry USB ....CCS.... Wire ..40 A.. Speaker
RDC. . . . . . . . . . router . . . . . . . . . . Pi-USB------------USB TR3/TR4============SSR40==================Speaker
On connection connection Computer Cable ..Switch... Pair Solenoid Wires
Desk In to to
Home
Office
This is a lengthy solution, but most of the equipment already exists today in a modern house. The only thing that needs to be purchased is the 40 Amp SSR40 Solenoid. The Remote Desktop Connection (RDC) software already exists in every Windows computer. RDC can be used to remotely control the Raspberry Pi from the desktop of a Windows Computer.
This CCS in this "speaker" application can be connected to the SSR40 solenoid via the terminals TR3/TR4 of the CCS. But the SSR40 Solenoid differs from the previous applications in that it is NOT a "Powered load". Like many modern solenoids, the SSR40 needs its voltage to be supplied by the device that is controlling it (which is the CCS in this case). Fortunately, the CCS (even the CCS2) can provide a low voltage (2V-5V DC) power source for the SSR40. So the CCS2 can control an "Unpowered Load". Other examples of the CCS2 driving aN "Upowered Load" exist but they might be less familiar to many people.
Another solution is to treat the Speaker as if it were a "Powered Load" which it is. The simpler diagram of this solution is shown below:
Amplifier
Computer ||
running wireless wireless Raspberry USB ....CCS.... Speaker ||
RDC. . . . . . . . . . router . . . . . . . . . . Pi-USB------------USB TR3/TR4=============--====Speaker
On connection connection Computer Cable ..Switch... Wires
Desk In to to
Home
Office
In the diagram above, one of the wires from the Amplifier must be cut. Then another pair of wires must be connected to the CCS. The
exact wiring is described in more detail in the Installation Notes. This solution does not need any additional solenoid to be purchased.
The CCS2 itself is the whole solution.
Application Case I: 5v DC Doorbell circuit
Of the 3 models of the CCS, the simplest one, the CCS2 is usually inserted in a circuit that uses 5v DC. Furthermore, the circuit must have the 5V Power Supply beside the load (the chimes), not beside the doorbell switch. The former is called a "Powered Load". The latter is called a "Powered Switch". Many Doorbell chimes serve a front door and a back door. Such Chimes are always powered by a "Powered Chime" which is a "Powered Load". A question arises: "Why use a CCS if the doorbells function just fine "as is"? The CCS permits a computer to also be used to turn on the doorbell chimes.
The PURPOSE of the CCS is to permit computer control of an electrical switch.
The Panel of the CCS can be set in fully operational model or not. When switch S6 of the CCS is Off, the CCS is not in fully operational mode. In this mode the CCS obeys the Remote Switch, just as if the CCS were not installed. In this mode, the computer switch is ignored.
The CCS2 will only power "Unpowerd Loads" that need 5 volts (5v0). The CCS1 and CCS3 will handle a range of AC and DC voltages. Much more is said later about how the CCS devices address the myriad Load Voltages that one encounters in a building's switches. For more information, see the heading: Measuring the Load's Voltage.
SAFETY FIRST
The only type of switched circuit that the CCS cannot easily handle is a case of AC line voltages of 110v AC or as high as 240v AC. These voltages can easily be deadly. In these cases, you are advised to hire a professional electrician. Please do this for safety's sake. Voltages under 25 volts are much less dangerous. The CCS devices can handle the high voltages, but an electrician should do the installation.
AC/DC Solenoids From the Orient
Many computer controlled switches (like the CCS devices) for AC line voltages (such as 110V AC) use an external solenoid that is controlled by 5v dc. Any of the 3 CCS switches can drive most of these solenoids with 5v DC. This is because 5v-driven solenoids are very compatible with all 3 CCS devices, even the CCS2. BC-Robotics (Source 03) provides a small range of solenoids such as the 40 A solenoid, shown below, (at a cost of CAD$15.95) which is described in Source 04. A full range of inexpensive solenoids are available from SparkFun. A datasheet describing such solenoids can be seen at Source 05. Even 3 Phase 240v AC solenoids (controlled by 5v dc) can be seen in Source 05. This same Datasheet is locally stored on the WebMaster's website at Source 06, in case the Datasheet at SparkFun is moved to a different website location by them.
(To enlarge .....Click it)
ssr-40 40 A solenoid
The CCS2 model of the Computer Controlled Switch
The CCS2 is the most common version of the CCS. It is the least expensive to buy and is the simplest to install. The CCS has been designed with the Raspberry Pi computer in mind. But a Windows, Apple or Linux PC can also be used to control a CCS. A USB port on any of these PCs can be used to control a CCS. The prerequisites of the situation (to use a CCS2) are:
- the switched circuit must use 5 V DC
- the switched circuit must use a "powered load" (not a "powered switch").
- the computer (that will control the load via the CCS), e.g. a Raspberry Pi, must have a usable USB port.
- the USB cable used must extend from the computer (e.g. the Raspberry Pi) to the CCS.
- the (doorbell) switch must be unlit, a lit doorbell switch will need to be replaced by one that is unlit.
Computer Controlled Switch (CCS)
The schematic drawing (shown below) is included to show other electronics designers how the CCS has been designed. It is not necessary to read nor understand this schematic drawing in order to use the CCS devices.
Note that the drawing below (on the left) has deprecated (replaced) an older schematic (the older one was dated 2021CMar7) for the CCS (shown next).
The drawing below illustrates how the CCS switch is connected to the Remote Switch and the Load. It is a generic drawing that includes all of the cases: Powered Switch, Powered Load and even the CCS2 that operates without a power supply. In the case of the CCS2, Relay A is not included and Relay C is replaced by a simpler relay with only 1 set of contacts (i.e. only one line is switched).
To make use of the generic schematic below, simply ignore or cross out either the Powered Switch or the Powered Load to make the drawing agree with your situation. If you are using the CCS2, ignore or cross out the power supply circuitry (leaving only the top set of points of relay B.) The schematic should now agree with your electric circuit and the model of CCS that you are using.
(To enlarge .....Click it)
CCS Schematic
Source 08 "Derivation of the CCS Schematic Ver F" is a text document that describes in detail the thought process that resulted in the above schematic for the CCS. It also describes the evolution of the greatly simplified CCS2 model.
Panel of the CCS
The panel of the CCS1 is shown below. It is the most sophisticated model of CCS. The CCS2 has a much simpler panel (shown after the CCS1).
SWITCH S11 LOAD
TR1 Red O S9 O Red TR3
Yel O S8 O Yel
TR2 Grn O PB0 S7 PB1 O Grn TR4
Vio O S6 O Blue
S5 O White Lext
S4
U S3
S S2 O Yel TR5
B Grn O PB2 S1 O Grn 15v AC Connector
O Vio TR6
The CCS1 Panel
************************************************
SWITCH LOAD *
S9 *
TR1 S8 TR3 *
S7 na *
TR2 S6 TR4 *
S5 O Blue *
S4 O White Lext *
U S3
S S2 *
B S1 *
************************************************
The CCS2 Panel *
************************************************
The various terminals, connectors and LEDs of the CCS2 are explained below:
- TR1 and TR2 are terminals for the wires going to the "Remote Switch".
- TR3 and TR4 are the terminals for the load wires (to the chimes in the case of the doorbell).
- The USB is the connector for the USB cable attached to the computer.
- Switch S3 is ON so that the Remote Switch state can be sensed when the "Remote Switch" is Unpowered.
- Switch S5 provides DC voltage (from the USB) to the Load when the "Load is Unpowered".
- Switch S6 is ON to tell the CCS2 that the panel is fully operational.
Turn S6 Off to disable (ignore) the Computer Switch (Dusb).
- Switch S7 is ON to tell the CCS2 that the CCS power is provided by the USB cable.
- Switch S9 is ON so that the CCS knows when it is a "Powered Load".
- The other (DIP) switches S1, S2, S4 and S8 are unused on the CCS2.
- The White LED is ON to show that the CCS2 is fully operational (i.e. the computer Switch is active).
- The Blue LED is ON to show that the load is a "Powered Load".
- The Blue LED is turned OFF when the Load is turned ON by either the (doorbell?) push switch or by the computer.
A normal doorbell switch is a spring-loaded push-button that is only ON while it is depressed.
The computer switch (Dusb) is more like a normal ON/OFF switch. After the computer turns the Dusb switch
ON, the computer's Dusb switch (and the Load) will stay ON until the computer turns the Dusb switch OFF.
- The Push-Button Switch should be pushed to see whether the "Remote Switch" is providing Positive or Negative voltage
when the "Remote Switch" is depressed. The RED LED indicates "Positive" DC Voltage, the Green LED indicates "Negative" DC
voltage. When both the RED and the Green LEDs are on, the Remote Switch" is providing AC voltage
One switch is noticeably missing on the CCS2 is switch S11. The S11 switch is needed in the non-CCS2 models because the
power to the load is either AC or DC in these models. Furthermore the switching of the load is different whether the Load
is powered or not. Switch S11 must be set according to whether the Load is Powered or Not. It would be easier and less
expensive to provide two models, an AC model and a DC model of the CCS. But the problem is that many people installing
the CCS would not know which one to buy. This is because a CCS is needed to determine (figure out) which one to buy.
Perhaps the cost of manufacturing the CCS will be the deciding factor. The author of this design doesn't want to tell
the future owners that they should first buy an AC model and a DC model. Then just return the one that wasn't needed.
That decision will be put off to another day.
For any technicians who have examined the above schematic, the "Open SW Sensor" and the "Blink Circuit" are not needed and are not included (or an ultra-simple version is included) in the CCS2.
CCS switches
In all models of the CCS there are 8 tiny DIP switches that must be set up correctly at installation time. DIP switch # 7 is unused. This is because models CCS1 and CCS3 deal with DC voltages higher than 5V and all AC voltages. These models keep the switched voltages separate from the logic voltages. A more complex switch (not a tiny DIP switch) is needed for S7 in the cases of CCS1 and CCS3.
Switch Usage
S1,S2, S4 and S8 are all used to drop a number of volts going to the Load. S1 drops 1.4v, S4 drops 5.6v etc
S3 is used only by the CCS2 model. It must be Closed if the "Load is Powered". Close S3 to pass 1.4 volts
(from Vusb) at .1 mA to the Power Sensor of the Remote Switch.
S5 is closed when POWdc is needed by the Load, so the CCS2 can provide power to an Unpowered Load.
S6 is closed (Pfull is True) when the Panel is fully operational (CS is active and can turn on the Load)
S7 is used to tell the CCS that the Load must be powered by a DC Voltage (Not an AC voltage)
S11 must have it's contacts shorting together when it is a "Powered Load". On the schematic, this is
shown by the "lever" of the switch being Down.
CCS2 Schematic
(To enlarge .....Click it)
hir_CCS2_E.odg Schematic for the CCS2
Pico Logic in CCS2
To use the CCS, you don't need to understand any of the computer logic described below. Feel free to skip these logic paragraphs. The names and meanings of each logic element in the CC2 are shown below:
Name Meaning of Logic Element of this Name
------ ---------------------------------------------
Blink Blinks on/off at about 1 Blink/Sec (but might be always On [True] in CCS2)
CS Computer Switch is ON
Dusb Computer Data USB requests to switch On the Load
Gnd All Logic is measured wrt Gnd [False]
Gusb Ground in the USB cable
LSW (A switch is On) i.e. (Remote switch is On) or (Pfull and Computer Switch [i.e. Dusb] is On)
The Load should be truly On [Remote Switch, Computer Switch and Pfull all agree that the Load should be On]
LEDwht white LED is ON: CCS Panel is fully operational. When Off, the Computer Switch is ignored).
LEDblu blue LED is ON: (Constant On: Load is not powered) or Blinking: (Load is visibly On (Lb) AND (Not Powered Load)
Pload Load type is "Powered Load"
Pfull True if DIP switch S6 is On [Panel is fully operational]. If S6 is Off, the Computer Switch is ignored.
RS Remote Switch is ON
Vusb always True (source of True logic) in the USB Connector. It is also the Source of Power when the Computer
Switch is On and the Load needs DC power to function.
The logic in the CCS2 is performed by the Pico Processor as shown below:
Blink Square Wave: Blinks on/off at about 1 Blink/Sec (but might be always On [True] in CCS2)
Dusb is either in the state that the Computer Switch is requesting or
the computer has sent a command to the Pico that the Computer Switch is On.
Gusb is Ground in the USB cable
Pload is the state of DIP switch S9 showing that the Load is Powered
Pfull is the state of DIP switch S6 showing that the Computer Switch should NOT be ignored.
RS is the state of the Remote switch
Vusb always True (a source of Power and True logic) in the USB Connector
************** Logic "Above" is CCS2 Logic, Logic "Below" is Pico Logic **************
CS Computer Switch is ON (derived from Dusb)
LSW = RS + ( Pfull . CS )
LSWdc = LSW . POWdc
LSWac = LSW . Not(Powdc)
FILLblu = LSW . Pload . Not(Blink)
LEDblu = BLink . LSW + FILLblue + ??(was Cpow) . Not(LSW)
LEDwht = Pfull
******************************************************************************************
NB Shouldn't use DC relay to switch an AC load *******************************************
******************************************************************************************
Measuring the Load's Voltage
A new concept used in the CCS is measuring the Load's Voltage in "blinks". The more expensive CCS models measure the Load's voltage and display it to the operator, on the CCS Panel, by making a LED blink a certain number of times. You just count the blinks.
One might think that "1 blink" means "1 volt". This is almost true. Actually "1 blink" means "1.4 volts" which is quite close to "1 volt". Lets say that the LED blinks 10 times. This means the Load's Voltage is actually 14 volts. But the CCS suggests that the voltage is said to be "10 blinks" instead of 14 volts. One might ask "Who cares what the Load's Voltage is". Well, when the computer provides the Voltage, it must provide nearly the exact correct voltage to the Load. This is alsolutely necessary when the Load is Powered by the Remote Switch. The problem is that the Power Supply accompanying the CCS1 (and CCS3) will be a 14 (or 15) volt AC Power Supply. This AC Power Supply can provide up to "10 Blinks" of Voltage. This will probably be too high a voltage for the Load. So you must know your Load's required Voltage.
During installation, the CCS1 and CCS3 will measure the Load's Voltage. . . Perhaps your Load's Voltage is "6 Blinks" (which is actually 8.4 Volts). So the Maximum Voltage from the CCS AC Power Supply is "4 Blinks" too high. This is because 10 - 6 = 4. The purpose of the TOTEM POLE switches is to reduce the voltage. This is done in increments of 1.4V (which is in groups of "1 Blink".) The CCS "AC Supply Voltage" can be reduced by "4 Blinks" by closing the switch S4. Yes S4 will drop the voltage by "4 Blinks" which is the required voltage reduction of 8.4V (because 14v - 5.6v = 8.4v). After closing S4, this reduced voltage is exactly the required Load Voltage of your switched circuit. Don't worry if you don't completely understand this. The CCS Installation Procedure simplifies it.
The four diodes that are used to drop 1.4 volts are normally used as a full-wave rectifier (FWR) as shown below on the left. The Totem "diamond" (shown on the right) is simply a normal FWR "diamond" (shown on the left) after its bottom part (the lower 2 diodes) has been rotated 180 degrees on a vertical axis. Note: after changing its bottom half, each unit of the totem device cannot be wired incorrectly. LOL
In fact, to install the CCS2, there is not any need to reduce any voltage, because the CCS2 only furnishes 5V DC to the LOAD (An AC Load is not supported). For Loads needing voltages other than 5V DC, install the CCS1 or CCS3.
The CCS installation instructions will show you how to hook up the SWITCH and LOAD wires correctly (with the correct polarity). This ensures that the CCS supplies the correct type of voltage (AC or DC) as well as the correct number of volts. It even helps you correct cases of wrong polarity. When using a CCS1 or CCS3, one other thing that you don't need to worry about is whether your Load's Voltage is AC or DC.
The instructions that come with the CCS even show you how the CCS1 or CCS3 can detect wrong polarity. Then it will show you how to connect the wires to the terminals to correct any polarity issues.
Pi Pico
The Pi Pico shown below is the tiny inexpensive microComputer (in the CCS) that "talks" to the computer. It also is the brains of the CCS. It examines the switches and controls all the LEDs and relays in the CCS. After installation, it does all the work for you.
(To enlarge .....Click it)
PiPico.jpg
Buffers for the Pi Pico
The text under this heading is only for electronics technicians. The Pi Pico is very sophisticated, but has some serious electronic shortcomings. One shortcoming is its poor ability to drive any electronic devices other than logic gates. To overcome this weakness, buffer gates need to be used to drive electronic devices such as LEDs or relays. The article 156 in Source 07 by this Webmaster recommends the use of the ...AHC541N gate as a 541 AHC buffer for the Pi Pico outputs. Furthermore the input pins of the Pi Pico must never "see" voltages higher than Vpico (i.e. 3v3 which is the Vcc for the Pi Pico) plus delta. When 3v0 is the Vcc for the ...AHC541, a True (i.e. 1 = high) input is any voltage over 2.1v; a False (i.e. 0 =low) input is any voltage under 0.9v . How to guarantee that the input levels are kept within tolerance? The outputs driving ...AHC541 gates (using a Vcc =3v0) should be protected with output clamps as follows:
clamp an excessively high input by passing current through a diode towards + 2v1.
the input gate won't see a voltage higher than 2v8
clamp an excessively low input by passing current through a diode from + 0v9
the input gate won't see a voltage lower than 0v2
These diode clamps guard against voltage extremes (but not against high frequency transients).
NOTE that the diode clamps shown below protect for Vcc=3v3 as well
HC Input 3v0 Protection Vcc=3v0
|
max |
high protection level 2v8__________| high
| high
| high
| high high
2v1 2v1----------|--------------threshold
__|__ | ?
^ __|__ ?
/ \ | \_ ?
----- | \ ?
unprotected | protected | | ?
---------- ---|--------------------| Gate |-----------output
input __|__ input | | ?
^ | _/ ?
/ \ |____/ ?
----- | ?
| | ? low
0v9 0v9----------|--------------threshold
| low
| low
min | low
low protection level 0v2__________| low
|
0v0___|___
_____
___
v
How to provide the 1V4 for the "Remote Switch" Power Sense circuit?
The solution is up to the electronics technician who first creates a prototype of this circuit.
Installation of the CCS2
The installation instructions have not yet been well-documented. Furthermore, none of the software has been written. Source 02 by the Webmaster shows some of the initial considerations and some initial thoughts about the installation of an earlier version of the CCS1. Beware that some of the circuitry and names of logic elements have been deprecated.
References
Books/Newspapers
Books/Newspapers 01: none
YouTube Videos
Source V01: ....Pico Reading Temperature ..... 
by "LearnElectronics" seen on 2021CMar10 (thanks to M. Asper)
Web Sites
Web Source S158:01: Raspberry Pi Pico BOARD Datasheet
by Raspberry Pi Association
Web Source S158:02: Computer Controlled Switch ver C
by D@CC on 2021BFeb28
Web Source S158:03: Solenoid Supplier: BC-Robotics
by D@CC on 2021BFeb28
Web Source S158:04: 40 A 380V AC Solenoid SSR40 from BC-Robotics
perused by D@CC on 2021CMar03
Web Source S158:05: Solenoid DataSheet from SparkFun
perused by D@CC on 2021CMar03
Web Source S158:06: Solenoid DataSheet from SparkFun (local copy)
perused by D@CC on 2021CMar03
Web Source S158:07: Article 156 Pi Pico via a Pi uart
by D@CC on 2021CMar03
Web Source S158:08: Derivation of the CCS Schematic Ver F
by D@CC on 2021CMar03
Web Source S158:09: Ti SN74AHC541N IC Data Sheet
revised by ti on 2015ISep
Web Source S158:10: PI: Monitor Freezer Temperatures
(and other similar) 11th Mar 2021 by Ashley Whittaker
Web Source S158:11: Airmeter on GitHub (Monitor Remote Temperature)
by Camden 12th March 2021
Web Source S158:12: PIO on the RP2040: Bit Banging
Click "What is PIO" by Alex Bate 2021C Mar 09
Web Source S158:13: PIO on the Pico: Bit Banging
from HackSpace by Ben Everard Jan 2021
Web Source S158:14: (Non-Pico) RP2040 Boards
from Raspberry Pi Foundation on Mar 2021
Created 2021 C Mar 02
Updated 2021 D Apr 16
(c) ICH180R2 Corp
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