PAGE 1: MAIN POWER
PAGE 2: 12V SUPPLY GOLF CART MOTOR
PAGE 3: ELECTRICAL CABINET
PAGE 4: BRAKE/WICKED RELAYS PAGE 5: AMP SEAL HEADERS
PAGE 6: PLASTIC TUBING COVERED ELECTRIC HARNESSES
PAGE 7: PLASTIC TUBING COVERED ELECTRICAL HARNESSES/MUTLI-WIRE CABLES
PAGE 8: BRAKE ACTUATOR/ WICKED STEERING/ LCD/ MISC. FRONT CONNECTIONS
TABLE OF CONTENTS:
-+
6V
6V
6V
6V
6V
6V
BATTERY BANK
CHARGER OUTLET
+
+
+ -
+-
- +
- +
- +
- +
+
-POS
NEGA2
A1
F1 F2
+-
GOLF CART CONTROLLER
LOCATION: Under Seat/Back of CartDRAWING DESCRIPTION: Main PowerDRAWING NUMBER: 1
(TO GOLF CART MOTOR)
48V+(TO +48V - 12V DC-DC)
TO CONTROLLER 23-PIN AMP SEAL HEADER
SOLENOID CONNECTOR
A2(TO 48-12V
DC-DC)
TO GOLF CART 23-PIN AMP SEAL HEADER
A1 F1 F2 A2
48V+ (to fuse on stock)
LOCATION: Under Seat/Back of CartDRAWING DESCRIPTION: 12V SUPPLY/GOLF CART MOTORDRAWING NUMBER: 2
12V -+
TO PLASTIC TUBE 2 (Wicked -PWR)
(pg 6)
TO CABINET(pg. 3)
BRAKE RELAY
WICKED RELAY
GOLF CART MOTOR
F1 F2
A1 A2
(FROM GOLF CART CONTROLLER)
(FROM GOLF CART CONTROLLER)
A1F1
F2
A2
LOCATION: Back of CartDRAWING DESCRIPTION: ELECTRICAL CABINETDRAWING NUMBER: 3
COMPUTER 48V DISCONNECT
BRAKE/STEERING
POWERPOWER
COMPUTER WICKED
ISSUEBRAKE ACTUATOR
SABERTOOTH
FANFA
N
ETHE
RNET
SWIT
CH
TB(REAR)48V-12VDC-DC
5V 3VCOMPUTER PWR
FAN
DRIV
E
USB
USB
HDMI
TO CONTROLLER 23-PIN AMP SEAL HEADER
(same as on page 1A)
TO GOLF CART 23-PIN AMP SEAL
HEADER
TO DASHBOARD & SENSORS 35-PIN AMP SEAL
HEADER
TO FRONT OF
CART
USBHUB
x3
+++
+++
++
+++
+++
++
+Vin
CASE
-Vin
+Vo+Vo+SPC
TRIM-S
-Vo-Vo
+++ +P2 P2 P1 P1
CASE GND
+++ + +++ +
+++ + +++ +
NC Trim 0V +Vo
Vin
GND
Ctrl
Case
GND
Vin
Ctrl
Case NC +Vo
Trim 0V
+++ + +++ + +
+++ + +++ + +
08 07 06 05 04 03 02 01 P2
08 07 06 05 04 03 02 01 P1
+++
PWRGND
PWRGND
LED
PWRGND
GND
PWR
To TB01-
To TB
01+
FROM 48V Disconnect
FROM Golf Cart Controller A2
KEY: = Behind Board/Panel = Given Electrical Harnesses = Behind and Given Electrical Harness
ETHERNET
ETHERNET
Com
p. P
CB C
able
FROM Rear Solenoid
TO +48V DC-DC
CPU_FAN
WIFI
Ant
enna
F_USB2 F_USB1 PW
Drive
Pow
erSe
rial A
TA
Serial ATA
ATX_12V
S2S15V0V
+++
+
M1AM1BB+B-M2AM2B
++
TO Brake/Wicked Coil
LED
PWRGND
FROM TB (REAR) P1 T7
RED To Brake/Wicked Power Switch BLK To Wicked /Brake Coils
(behind)
FROM Brake RelayFROM -12V Extra Battery
TO Plastic Covered Tube 2
LOCATION: Back of CartDRAWING DESCRIPTION: ELECTRICAL CABINET RELAYSDRAWING NUMBER: 4
BRAKE RELAY
`
WICKED RELAY
TO WICKED +PWR
TO B+ (SABERTOOTH)
FROM +12V BATTERY
FROM BRAKE/STEERING POWER SWITCHFROM TB (REAR) P2 T7
LOCATION: Back of CartDRAWING DESCRIPTION: AMP SEAL HEADERSDRAWING NUMBER: 5
PIN1PIN2PIN3PIN4PIN5PIN6PIN7PIN8PIN9PIN10PIN11PIN12PIN13PIN14PIN15PIN16PIN17PIN18PIN19PIN20PIN21PIN22PIN23
AMP
SEAL
23-
PIN
HEAD
ER
AMP1AMP2AMP3AMP4AMP5AMP6THROT_OUTTHROT_GNDTHROT_PWR_OUTAMP10AMP11AMP12AMP13THROT_VTACHAMP15AMP16AMP17AMP18AMP19AMP20AMP21AMP22AMP23
TO CONTROLLER
PIN1PIN2PIN3PIN4PIN5PIN6PIN7PIN8PIN9PIN10PIN11PIN12PIN13PIN14PIN15PIN16PIN17PIN18PIN19PIN20PIN21PIN22PIN23
AMP
SEAL
23-
PIN
HEAD
ER
AMP1AMP2SOLENOIDAMP4AMP5AMP6THROT_INTHROT_GNDTHROT_PWR_INAMP10SOLENOIDAMP12AMP13THROT_VTACHAMP15AMP16AMP17AMP18AMP19AMP20AMP21AMP22AMP23
TO GOLFCART
PIN1PIN2PIN3PIN4PIN5PIN6PIN7PIN8PIN9PIN10PIN11PIN12PIN13PIN14PIN15PIN16PIN17PIN18PIN19PIN20PIN21PIN22PIN23PIN24PIN25PIN26PIN27PIN28PIN29PIN30PIN31PIN32PIN33PIN34PIN35
AMP
SEAL
35-
PIN
HEAD
ER
CHECK_LED_OUTGNDBRAKING_LED_OUTSTEERING_LED_OUTREADY_LED_OUT5VTHROTTLE_LED_OUTGNDM_LCD_RSM_LCD_FM_LCD_DB4M_LCD_DB5M_LCD_DB6M_LCD_DB75VM_ESTOP3.3VT_ACTUATOR---5VGNDM_GPSF_DIFF_PF_DIFF_NTO_DIFF_PTO_DIFF_NS_POT3.3VGNDM_AUTO_MAN3.3VGND5VGNDT_MAG
DASHBOARD AND SENSORS
LOCATION: Under Cart (Back to Front of Cart)DRAWING DESCRIPTION: PLASTIC TUBING COVERED ELECTRICAL HARNESSESDRAWING NUMBER: 6
REAR OF CART/ ENCLOSURE FRONT OF CART
PLASTIC COVERED TUBE 2 (zip tied in rear of cart)FROM M1A
-12V BATTERY
FROM WICKED RELAY
TO Braking Actuator Connector
TO WICKED PWR +
FUSE
FROM M1B
TO WICKED PWR -
Smaller Plastic Tube 2 Extender
Extender
Shrink Tube
Shrink Tube
TO WICKED LED+ 12V Power On TO WICKED CONNECTOR
KEY: = INSIDE PLASTIC COVERED TUBE
Smaller Plastic Tube 3
LOCATION: Under Cart (Back to Front of Cart)DRAWING DESCRIPTION: PLASTIC TUBING COVERED ELECTRICAL HARNESSES/MUTLI-WIRE CABLESDRAWING NUMBER: 7
REAR OF CART/ ENCLOSURE FRONT OF CART
Smaller Plastic Tube 3B
Smaller Plastic
Tube 3A
MIDDLE OF CART
PLASTIC COVERED TUBE 3 (DIRTY ONE)
PLUGS
TO STOCK REVERSE BEEPER CONNECTOR
TO KEY IGNITION
FWD/REV CONNECTOR
TO REV/FWD SWITCH
TO SOLENOID CONNECTOR (PG1)
TO SOLENOID + TERMINAL
FUSE
TO C
ONTR
OLLE
R 23
-PIN
AM
P SE
ALHE
ADER
TO C
ONTR
OLLE
R 23
-PIN
AM
P SE
ALHE
ADER
TO STEERING POT
TO LCD1, LCD2, A/M SWITCH, ESTOP, and LED (not using anymore) CONNECTORS
MULI WIRE CABLES
4 CONNECTORS UNDER THE CART
TO BRAKING POT
TO WICKED CNTL INPUT/TORQUE SENSOR
Smaller Plastic
Tube 3C
FWD/REV CONNECTOR
TO GOLF CART BRAKE
THROTTLE CONNECTOR
TO THROTTLE ENGAGE BUTTON (pin 3 and 4)
1
2
3
4
KEY: = INSIDE PLASTIC COVERED TUBE
LOCATION: Front of CartDRAWING DESCRIPTION: BRAKE ACTUATOR/ WICKED STEERING/ LCD/ MISC. FRONT CONNECTIONSDRAWING NUMBER: 8
LCD
USB N/C
PWR INHDMI
HDMI From Cabinet
USB From Cabinet USB Hub
To Mouse
To Key Board WICKED MOTOR
WICKED STEERING
PWR IN
WICKED PWR CONNECTOR
(FRO
M Sm
all Tu
be 2
) W
ICKE
D PW
R +
GND
N/C
CON6
Torque SensorBRAKING
ACTUATOR
Braking Actuator Connector
TO Brake POT
THROTTLE ENGAGE BUTTON
3 4
FROM THROTTLE
CONNECTOR
SS2
Wicked LED2Wicked LED1
SS1
LOCATION: Front of CartDRAWING DESCRIPTION: Ultrasonic WiringDRAWING NUMBER: 9
MB7
001
12
AN45
V+GND
MB7
001
12
AN45
V+GND
MB7
001
12
AN45
V+GND
MB7
363
12345
V+GND
MB7
363
12345
V+GND
MB7
363
12345
V+GND
MB7
363
12345
V+GND
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
A0 (Arduino)
A1 (Arduino)
A2 (Arduino)
A3 (Arduino)
A4 (Arduino)
A5 (Arduino)
A6 (Arduino)
2 (PWM from Arduino)
1 2 3 4 5 6
1 2 3 4 5 6
A
B
C
D
A
B
C
D
Date: KiCad E.D.A. kicad 4.0.1-stable
Rev: Size: A4Id: 1/3
Title: File: APM_PCB_v1.schSheet: /
ARD
UIN
O D
UE
0(RX) 01(TX) 1
2 23 34 45 56 67 7
8 89 9
10 10
20(SDA) 20
3030
4040
5050
A0A0
11 11
21(SCL) 21
3131
4141
5151
A1A1
12 12
2222
3232
4242
5252
A2A2
13 13
2323
3333
4343
5353
A3A3
14(TX3) 14
2424
3434
4444
A4A4
15(RX3) 15
2525
3535
4545
A5A5
16(TX2) 16
2626
3636
4646
A6A6
17(RX2) 17
2727
3737
4747
A7A7
18(TX1) 18
2828
3838
4848
A8A8
19(RX1) 19
2929
3939
4949
A9A9
5V5V
+5V.
5V.
A10A10
A11A11
DAC0A12
DAC1A13
CANRXA14
CANTXA15
(N/C)N/CGND GND
VINVIN
+5V.
.5V
..
GND.GND.GND..GND.
GN
D...
GN
D.
GN
D...
.GN
D.
SDA1 SDA1SCL1 SCL1
RESETRESE
AREF AREF
IOREFI/OR
3.3V3.3V
ARD
UIN
O D
UE
0(RX) 01(TX) 1
2 23 34 45 56 67 7
8 89 9
10 10
20(SDA) 20
3030
4040
5050
A0A0
11 11
21(SCL) 21
3131
4141
5151
A1A1
12 12
2222
3232
4242
5252
A2A2
13 13
2323
3333
4343
5353
A3A3
14(TX3) 14
2424
3434
4444
A4A4
15(RX3) 15
2525
3535
4545
A5A5
16(TX2) 16
2626
3636
4646
A6A6
17(RX2) 17
2727
3737
4747
A7A7
18(TX1) 18
2828
3838
4848
A8A8
19(RX1) 19
2929
3939
4949
A9A9
5V5V
+5V.
5V.
A10A10
A11A11
DAC0A12
DAC1A13
CANRXA14
CANTXA15
(N/C)N/CGND GND
VINVIN
+5V.
.5V
..
GND.GND.GND..GND.
GN
D...
GN
D.
GN
D...
.GN
D.
SDA1 SDA1SCL1 SCL1
RESETRESE
AREF AREF
IOREFI/OR
3.3V3.3V
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
20 20
3030
11 11
21 21
3131
12 12
22 22
3232
13 13
23 23
3333
14 14
2424
3434
15 15
2525
3535
16 16
2626
17 17
2727
18 18
2828
19 19
2929
M1AMPSEAL-35
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
2020
11 11
2121
12 12
2222
13 13
2323
14 14
15 15
1616
1717
1818
1919
M2AMPSEAL-23
AMP15THROTTLE_OUT
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
2020
11 11
2121
12 12
2222
13 13
2323
14 14
15 15
1616
1717
1818
1919
M3AMPSEAL-23
To Controller
VTACH
AMP17
AMP18
AMP19
AMP20
AMP21
AMP22
AMP23 THROTTLE_GND
AMP14AMP6
AMP13AMP5
AMP12AMP4
AMP11AMP3
AMP10AMP2
AMP1THROTTLE_PWR
To Cart
VTACH
AMP17
AMP18
AMP19
AMP20
AMP21
AMP22
AMP23
AMP1THROTTLE_PWR
AMP2
THROTTLE_IN
THROTTLE_GNDAMP15
AMP14AMP6
AMP13AMP5
AMP12AMP4
AMP11AMP3
AMP10
STEERING_POT
STEERING_DACTHROTTLE_DAC
STEERING_POT
STEERING_3.3V_REF
APM_PCB_v1_sheet2
APM_PCB_v1_sheet2.sch
APM_PCB_v1_sheet3
APM_PCB_v1_sheet3.sch
C14
10uF
GND
R231.5k
VTACH_PWM3.3V
TORQUE_SENSOR_TO_ADC
BRAKE_PWM
BRAKE_SABRE
D1
D
D2
D
+12V+12V
LIGHT_CONTROL
SOUNDER_CONTROL
ESTOP
ESTOP
R27
100k
+3.3V
1 2 3 4 5 6
1 2 3 4 5 6
A
B
C
D
A
B
C
D
Date: KiCad E.D.A. kicad 4.0.1-stable
Rev: Size: A4Id: 2/3
Title: File: APM_PCB_v1_sheet2.schSheet: /APM_PCB_v1_sheet2/
+5V
C2
.1uF
C1
10uF
GND
VBIAS 1
GND 2EN3
VIN4 VREF 5
U1REF2033AIDDCR
R2
10k
R12k
R322k
R433k
+5V
GND
C4
.1uF
C3
10uF
GN
D
GND
R522K
R6
33k
THROTTLE_DAC
THROTTLE_OUTVOUTA 1
-IN_A2+_IN_A3
V-4
+IN_B5
-IN_B6
VOUTB 7V+8
U2
OPA2365AID
GND
VOUT 1
V-2
+IN3
-IN4
V+5 U3
OPA365AIDBVR.55V
VREF.55V.55V
+5V
C6
.1uF
C5
10uF
GN
D
3.3V
REF2033
OPA365
VREF
.55V
VOUTA 1
-IN_A2+_IN_A3
V-4
+IN_B5
-IN_B6
VOUTB 7V+8
U4
OPA2365AID
+5V
C8
.1uF
C7
10uF
GN
D
GND
TORQUE_SENSOR_IN_N
TORQUE_SENSOR_IN_P
R1033k
R9100k
TORQUE_SENSOR_TO_ADC
R8100kR733k
Torque Sensor Buffers
Torque Sensor &Throttle DiffAmps
0.55V Buffer
(to controller)
+5V
GND
C10
.1uF
C9
10uF
GN
D
VOUTA 1
-IN_A2+_IN_A3
V-4
+IN_B5
-IN_B6
VOUTB 7V+8
U5
OPA2365AIDR1333kVREF.55V
R1910
R2010
STEERING_OUT_N
STEERING_OUT_P
R1775k
C11
20nF
STEERING_DAC
R1433k
R16 75k
R1533k
R1875k
C12
20nF
R12 22k
R11 16k
GND
3.3V
1.9097V
Steering Circuit
OPA2365
OPA2365
OPA2365R21
100k
GND
(pul
l-dow
n)
(ban
dpas
s)(b
andp
ass)
N.C1
A2
GND3
Y 4VCC5U6
SN74LVC1G17DBVR
+5V
GND
BRAKE_PWM
BRAKE_SABRE
Schmitt Trigger
Brake Level ShifterN.C1
A2
GND3
Y 4VCC5U7
SN74LVC1G17DBVR
GND
VTACH
VTACH_PWM3.3V
Schmitt Trigger
VTACH Level Shifter
R220
C13
0F
+3.3V
(to Arduino)
(to Sabretooth)
(from Arduino)
(from cart)
(to Wicked)
(to Wicked)
(from Wicked)
(from Wicked)
(to Arduino)
R241.5k
C15
10uF
GND
TS_IN_BUF_N
TS_IN_BUF_P
TS_IN_BUF_P
TS_IN_BUF_N
VREF1.65V
VREF1.65V
(from Arduino)
1 2 3 4 5 6
1 2 3 4 5 6
A
B
C
D
A
B
C
D
Date: KiCad E.D.A. kicad 4.0.1-stable
Rev: Size: A4Id: 3/3
Title: File: APM_PCB_v1_sheet3.schSheet: /APM_PCB_v1_sheet3/
1
23
Q1Q_NMOS_GSD 1
23
Q2Q_NMOS_GSDLIGHT_CONTROL SOUNDER_CONTROL
GND GND
LIGHT_LOW SOUNDER_LOW
R25220
R26220
Autonomous People Mover Voltage Shifting Circuits Overview Throttle Control The purpose of this circuit is to scale the DAC output of the Arduino Due to the voltages expected by the golf cart controller. The Due outputs .55V – 2.75V and the controller expects 0V – 3.3V. Notes: The 5V comes from the 5V power supply. The 3.3V will come from a voltage reference IC (TI’s REF2033). The REF2033 was chosen because it supplies a 3.3V and a 1.65V reference and we need both. The 1.65V reference is used in both the torque sensor and steering circuits. The first opamp is a buffer to isolate the impedance of the voltage divider circuit. The second opamp is in a differential configuration with an offset of .55V.
𝑉𝑜𝑢𝑡 = −𝑅𝑓𝑅𝑖𝑛
(𝑉𝑟𝑒𝑓 − 𝑉𝑖𝑛) 𝑇ℎ𝑟𝑜𝑡𝑡𝑙𝑒_𝑂𝑢𝑡𝑝𝑢𝑡 = −32 (.55 − 𝑉𝑖𝑛)
Concerns: The TLC277 is a precision opamp but is not rail-to-rail. Could we use a different opamp that would be better suited to get us down to that 0V rail? Solution: Use an OPA365 opamp. (Rail-to-rail, High performance)
U1A
TLC277/101/TI
+3
-2
V+8
V-4
OUT1
U1B
TLC277/101/TI
+5
-6
V+8
V-4
OUT7
0
V15Vdc
5V
0
5V
5V3.3V
V23.3Vdc
0
R110k
R22k
R3
33.3k
R4
22.2k
R5
22.2k
R6
33.3k
0
Vref
3.3V
0.55V
0
Throttle_Output
V30V
Vin
0
Vin
0
V
V
V_V3
0.4V 0.6V 0.8V 1.0V 1.2V 1.4V 1.6V 1.8V 2.0V 2.2V 2.4V 2.6V 2.8VV(VIN) V(THROTTLE_OUTPUT)
0V
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
3.5V
Steering Control (Updated circuit - Bridged) The purpose of this circuit is to drive the Wicked steering system. The Wicked system is controlled by a +/- 5V differential signal centered at 2.5V. This circuit converts a .55V – 2.75V Arduino Due DAC output to a +/- 5V differential signal centered at 2.5V. The 2.5V center is critical because the Wicked controller will throw an error code if it does not receive this. Notes: U1 is a buffer for the .55V reference. C1 and C2 are band limiting caps that may or may not be populated on the board depending on what kind of noise is observed. R13 is a pull down resistor for the DAC output. R14 and R15 are 10Ω resistors used to compensate for the potential capacitive load of the output (transmission lines). Concerns: The wicked module is looking for both signals to be 2.5V for a 0V differential. If these circuits aren’t perfect then the output of the two stages won’t cross at 2.5V.
0
0
U1
OPAMP
+
-
OUT
U2
OPAMP
+
-
OUT
V10Vdc
DAC_in
V33.3Vdc
0
3.3V
R110k
R22k
3.3V
0
.55V
R3
33kR4
33kR575k
R6
75k
OUT_N
R716k
R822k
0
3.3V
1.9097V
R9
33k
R12
75k
U4
OPAMP
+
-
OUTOUT_P
DAC_in
R1310k
0
C1
1n
C2
1n
R14
10
R15
10
R_LOAD1000k
V
V
V
Reference and gain calculations:
OUT_N Stage:
𝑂𝑈𝑇_𝑁 = − 𝑅𝐹𝑅𝐺 (𝑉𝑅𝐸𝐹 − 𝑉𝐼𝑁) (1) VREF determined by solving (1) for condition when DAC_in = .55V and OUT_N = 0V
0 = (𝑉𝑅𝐸𝐹 − .55) VREF = .55V Gain was determined by solving (1) for condition when DAC_in = 2.75V and OUT_N = 5V
5 = −𝑅𝐹𝑅𝐺
(. 55 − 2.75)
𝑅𝐹𝑅𝐺
= 5
2.2 = 75𝑘33𝑘
OUT_P Stage: A difference amplifier was used for the OUT_P Stage:
(2)
V_V1
0.4V 0.6V 0.8V 1.0V 1.2V 1.4V 1.6V 1.8V 2.0V 2.2V 2.4V 2.6V 2.8VV(DAC_IN) V(R_LOAD:2) V(R_LOAD:1)
0V
2.0V
4.0V
6.0V
Given the transfer function for a standard difference amplifier (2), the following steps were followed to obtain the desired circuit.
1. Set V2 = 3.3V because we already have a solid 3.3V reference. 2. Pick arbitrary values for two of the resistors. Say Rg = 22k and Rf = 75k 3. Substitute the two known Vin, Vout conditions into the diffamp transfer equation.
5 = (𝑅1+75𝑘𝑅1 ) (
22𝑘22𝑘+𝑅2
) 3.3 − 75𝑘𝑅1 .55 and 0 = (𝑅1+75𝑘
𝑅1) ( 22𝑘22𝑘+𝑅2) 3.3 −
75𝑘𝑅1
2.75 4. Solve system of two equations and two unknowns.
Result: VREF = 3.3V, R1 = 33kΩ, Rf = 75kΩ, R2 = 16kΩ, Rg = 22k
Hardware result with respect to ground: (Input not shown)
Hardware result single ended input to differential output: (C1 input – C2 output)
Potential bandpass cap estimate: 𝑓𝑐 = 1
2𝜋𝑅𝐶 say fc = 100Hz
𝐶 = 1
2𝜋100(75𝑘) = 21𝑛𝐹
Check that time constant isn’t too large: τ = RC = (75k)(21nF) = 1.59ms (not bad)
So a bandpass cap anywhere around 21nF should be effective.
Torque Sensor Circuit (Updated) The purpose of this circuit is to shift the differential signal from the torque sensor so that it can be read by an Arduino ADC. The differential signal has a range of +/- 5V centered at 2.5V. This differential signal is converted to a single ended value between 0 and 3.3V. Notes: This was first attempted with a single opamp, but then it was found that the input resistors were affecting the input voltage. This was believed to be due to a low impedance in the torque sensor circuitry. Because of this, and the fact that it is a differential signal, an instrumentation amplifier would be ideal to isolate the torque sensor. However, there is only a single supply which eliminates the ability to use an instrumentation amplifier IC. The following circuit was designed to have the high impedance of an instrumentation amplifier while converting from a differential to single ended signal.
Torque_sensor_+
Torque_sensor_-U6
OPAMP
+
-
OUT
U7
OPAMP
+
-
OUT
U8
OPAMP
+
-
OUT
RG5
100k
RG6
33k
RG7
100k
RG833k
Vout
1.65Vdc
0
V
V
V
V_V2
-3.0V -2.0V -1.0V -0.0V 1.0V 2.0V 3.0VV(DIFF+) V(DIFF-) V(VOUT)
0V
2.5V
5.0V
The following steps were accomplished to determine appropriate resistor values: Using the component names shown in the following circuit diagram (for ease of display and calculations):
Standard Kirchhoff’s Current Law gives the following two equations:
𝑉1 − 𝑉−
𝑅1=
𝑉− − 𝑉𝑜𝑢𝑡𝑅𝑓
→ 𝑉− =
𝑅𝑓𝑅1
𝑉1 + 𝑉𝑜𝑢𝑡
1 + 𝑅𝑓𝑅1
and
𝑉2 − 𝑉+
𝑅2=
𝑉+ − 𝑉𝑅𝑒𝑓𝑅𝑔
→ 𝑉+ =
𝑅𝑔𝑅2
𝑉2 + 𝑉𝑅𝑒𝑓
1 + 𝑅𝑔𝑅2
Set V- = V+
𝑅𝑓𝑅1
𝑉1 + 𝑉𝑜𝑢𝑡
1 + 𝑅𝑓𝑅1
=
𝑅𝑔𝑅2
𝑉2 + 𝑉𝑅𝑒𝑓
1 + 𝑅𝑔𝑅2
Move some terms around for readability:
𝑉𝑜𝑢𝑡 = (1 +
𝑅𝑓𝑅1
1 + 𝑅𝑔𝑅2
) (𝑅𝑔𝑅2
𝑉2 + 𝑉𝑅𝑒𝑓) − 𝑅𝑓𝑅1
𝑉1
An arbitrary value could then be used for VRef, but it would be better to set it to 1.65V. This is not very intuitive, but it’s due to the fact that the desired output should be 0V to 3.3V and 1.65V is the center of that range. This also results in a balanced circuit where Rf = Rg and R1 = R2 (this result will be shown in the following few steps).
𝑉𝑜𝑢𝑡 = (1 +
𝑅𝑓𝑅1
1 + 𝑅𝑔𝑅2
) (𝑅𝑔𝑅2
𝑉2 + 1.65) − 𝑅𝑓𝑅1
𝑉1
Pick arbitrary values for Rf and Rg. Say 33kΩ.
𝑉𝑜𝑢𝑡 = (1 + 33000𝑅11 + 33000𝑅2
) (33000
𝑅2𝑉2 + 1.65) −
33000𝑅1
𝑉1
Substitute desired use conditions into the transfer equation to obtain a system of two equations and two unknowns.
V1 = 5, V2 = 0, Vout = 0
0 = (1 + 33000𝑅11 + 33000𝑅2
) (33000
𝑅2(0) + 1.65) −
33000𝑅1
5
V1 = 0, V2 = 5, Vout = 3.3
3.3 = (1 + 33000𝑅11 + 33000𝑅2
) (33000
𝑅2(5) + 1.65) −
33000𝑅1
0
Solving the system of equations results in R1 = R2 = 100,000
Summary: VRef = 1.65V Rf = Rg = 33kΩ R1 = R2 = 100kΩ
Hardware result: Channel 1 (Orange) is differential input, Channel 2 (Blue) is output
Maybe a cap on the output of the circuit? (Channel 2 – Blue)
Vtach throttle encoding The throttle encoder appears to be, or at least function as, a hall effect sensor.
Figure 1 - VTach throttle encoder at fast speed
Figure 2 - VTach throttle encoder at slow speed
Arduinos PulseIn function can be used to measure the period of this signal which is directly related to the speed of the golf cart. This signal needs to be shifted from 0-5V to 0-3.3V for a digital pin on an Arduino Due.
Solution: Schmitt trigger buffer SN74LVC1G17 with 0 ohm resistor and cap on input (low pass filter)
TODO: Test on hardware.
Updates: Low pass filters were added on both the steering pot signal and the steering dac signal. (See PCB schematic)
