Hello,
I would like please to ask about a circuit I am building. It will have:
1 arduino Nano
5 servos
1 current sensor
1 nRF24L01
2 Shift registers connected to many LEDs
1 RPM sensor using the spark plug feeder
1 temperature sensor connected to the spark plug with its ring cable
1 hall sensor for speedometer
1 current sensor
So my question is, I have 1 battery pack of 12V and 3800 mAh which will feed all the components, for the servos I will connect each of them to a separate UBEC regulator voltage step down and the arduino directly to the 12V battery and taking 5V from arduino which will feed the shift registers, the temp sensor and the rpm sensor circuit. So should the servos GND be connected back to arduino GND or only the data wire should be connected to arduino Pin ?
Servos have 3 wires , (GND, 5V, SIGNAL). An arduino cannot send a SIGNAL to a servo WITHOUT the servo GND
because the GND is the RETURN for the SIGNAL. This rule is true of ALL devices controlled by an arduino. When
it is desired to have ISOLATION between a microcontroller and some device, OPTOCOUPLERS are used, in which
case the opto LED CATHODE is the RETURN. (a series current limiting resistor is required between the led +V and the led) . The opto TRANSISTOR is then used as the output device and has an ISOLATED GRN common with the
controlled device. This has been the standard microcontroller isolation method since the dawn of computers,
even before single chip microcontrollers were available because back then, the cost of replacing a damaged
computer I/O was >> than the current cost of an arduino. Before optos were available, relays provided the isolation. The decision to use isolation is one the designer makes based on the environment and any conditions
that may pose a risk of damage to the electronics. The use of the spark plug feeder and the term 'rpm' suggests this is an automotive application, in which case isolation is probably recommended. Since automotive electronics
is not my area of expertise I would have to defer to those who are more familiar with this subject. I can ,however
tell you that ATMEL has clearly stated that the ATMega328 is NOT recommended for automotive applications.
The ATMega328PB AUTOMOTIVE, however is designed for such applications.
elizabaths:
All voltage regulators work about the same. ... This can make a standard 7805 give any voltage between 5 volts and your supply volts. This shows how much regulators are the same. About supply voltage to a regulator. use voltage regulators in a circuit?
Always double-check the “OUT” voltage with a multi-meter prior to connecting your circuit up. ...
Most regulators have only 3 ports (IN/OUT/GND). ...
Excess voltage is dissipated as heat by the regulator, so take care when designing and using circuits.
I will not have to design my own regulators because I did and i connected it to a 9g mini servo which seems to have killed it, so i decided to use the UBEC of 5V output and 3.5A but my question is should I connect the grounds from one UBEC to the GND of arduino with the GND of the servo or just to the GND of the servo?
MODERATOR EDIT : the post quoted has been deleted because it had a hidden link in it. The link has been removed from the quoted text
raschemmel:
Servos have 3 wires , (GND, 5V, SIGNAL). An arduino cannot send a SIGNAL to a servo WITHOUT the servo GND
because the GND is the RETURN for the SIGNAL. This rule is true of ALL devices controlled by an arduino. When
it is desired to have ISOLATION between a microcontroller and some device, OPTOCOUPLERS are used, in which
case the opto LED CATHODE is the RETURN. (a series current limiting resistor is required between the led +V and the led) . The opto TRANSISTOR is then used as the output device and has an ISOLATED GRN common with the
controlled device. This has been the standard microcontroller isolation method since the dawn of computers,
even before single chip microcontrollers were available because back then, the cost of replacing a damaged
computer I/O was >> than the current cost of an arduino. Before optos were available, relays provided the isolation. The decision to use isolation is one the designer makes based on the environment and any conditions
that may pose a risk of damage to the electronics. The use of the spark plug feeder and the term 'rpm' suggests this is an automotive application, in which case isolation is probably recommended. Since automotive electronics
is not my area of expertise I would have to defer to those who are more familiar with this subject. I can ,however
tell you that ATMEL has clearly stated that the ATMega328 is NOT recommended for automotive applications.
The ATMega328PB AUTOMOTIVE, however is designed for such applications.
it is not actually a real automotive project, it is an RC car
"t is not actually a real automotive project, it is an RC car"
Somehow the word 'cool' is woefully inadequate to describe your project. I think "awesome" still leaves something to be desired. Let's try "HOLY SMOKES BATMAN ! That's SOME RC PROJECT !!! !"
Count me in. Anything you need in the way of electronics short of PCB layout let me know.! That includes schematic capture. Unfortunately they just changed my work laptop and I haven't tried the Orcad yet but I suspect it's not going to work. ExpressSCH works for a lot of stuff. I didn't see a schematic. Did you post one ?
You need to have at least 470uF filter cap across the 5V (+) line and GND. The should only be ONE GND unless you have decided to have isolation. Do you have a block diagram ? Do you have CAD drawing (2D) or (3D) of the car or a hand drawn drawing on an artists schetchpad from Michael's Arts&Craft supplies that shows wire run lengths ? Do you have a GOPRO or other video camera with 720P/1080P HD output or at least composite color
video ? Do you have a 5 Ghz video transmitter and OSD (on screen display) board with GPS ? (to measure speed)
Do you have a 5 Ghz video receiver with a video DVR to record the realtime received video ? What's the distance between Transmitter and Receiver of the NRF24L01 ? Do you have a way to track and display track position via GPS ? Are you using FPV goggles ? If so, do you have realtime video out for the goggles ?
What's the engine ?
Have you seen this ?
And this ?
raschemmel:
"t is not actually a real automotive project, it is an RC car"
Somehow the word 'cool' is woefully inadequate to describe your project. I think "awesome" still leaves something to be desired. Let's try "HOLY SMOKES BATMAN ! That's SOME RC PROJECT !!! !"
Count me in. Anything you need in the way of electronics short of PCB layout let me know.! That includes schematic capture. Unfortunately they just changed my work laptop and I haven't tried the Orcad yet but I suspect it's not going to work. ExpressSCH works for a lot of stuff. I didn't see a schematic. Did you post one ?
You need to have at least 470uF filter cap across the 5V (+) line and GND. The should only be ONE GND unless you have decided to have isolation. Do you have a block diagram ? Do you have CAD drawing (2D) or (3D) of the car or a hand drawn drawing on an artists schetchpad from Michael's Arts&Craft supplies that shows wire run lengths ? Do you have a GOPRO or other video camera with 720P/1080P HD output or at least composite color
video ? Do you have a 5 Ghz video transmitter and OSD (on screen display) board with GPS ? (to measure speed)
Do you have a 5 Ghz video receiver with a video DVR to record the realtime received video ? What's the distance between Transmitter and Receiver of the NRF24L01 ? Do you have a way to track and display track position via GPS ? Are you using FPV goggles ? If so, do you have realtime video out for the goggles ?
What's the engine ?
Have you seen this ?
And this ?
I thank you so much for the way you described my project and your interest
it can also be followed on facebook page
well I have lots and lots of ideas about it and what can be done with it but that will be developed after first prototype
about the video transmitter, yes i do have a video transmitter and receiver, i will be using an lcd display to see the picture from the car, i don't have yet a full circuit schematic but i have a schematic for the rpm LEDs which i have made with autodesk eagle and printed via jlcpcb in china
at the moment I am working on the controller software it is 70% done but i found out that i am over programming it by using a 12 positions rotary switch instead of 6 so tomorrow i will be buying the 6 positions rotary hope i find them available
information about the engine can be found on my blog in this link
the price is ok but the engine won't work it is small for 1:8 scaled cars mine is 1/4, but it would have been nice to put such an engine but you also would need to design a gearbox for it
I don't understand how they calculate power for scaled cars.
If your engine is 3.36kW then it is 4.5 hp.
If your car is 1/4 scale then 4*4.5= 18 ho which
isn't even close to full scale F1 hp. There must be a double standard.
raschemmel:
I don't understand how they calculate power for scaled cars.
If your engine is 3.36kW then it is 4.5 hp.
If your car is 1/4 scale then 4*4.5= 18 ho which
isn't even close to full scale F1 hp. There must be a double standard.
not really about the scale of f1
the engine i am using is a 3hp engine and it should be enough. The main challenge i have is that the clutch would be always engaged because of the not very very accurate 3d printed materials. In that case I would have to make my own manufactured clutch bell with bigger diameter where the clutches engages. Other than that I found solutions for the heat which coming from the engine to the gearbox structure and the floor or from the exhaust
raschemmel:
I don't understand how they calculate power for scaled cars.
If your engine is 3.36kW then it is 4.5 hp.
If your car is 1/4 scale then 4*4.5= 18 ho which
isn't even close to full scale F1 hp. There must be a double standard.
Drag scales with area, not size, speed scales with size, so drag x speed scales as
size cubed, and roughly power = drag x speed
so 4.5hp x 4^3 ~ 300hp. Seems reasonable.
[ whoops, drag goes with velocity squared, so is 4^2 times less in the 1/4 scale anyway, so
lets do this properly: ]
drag force = 0.5 * Cd x rho x v^2 x A (rho = density of air, Cd = drag coeff, A = frontal area)
Lets assume Cd = 0.7 (typical for F1 car - much of the drag is needed for downforce)
So at 200mph (90m/s), estimate A = 1.5, get drag force = 5.1kN, so power to
overcome drag = 90m/s x 5.1kN = 460kW = 605hp
This seems reasonable.
For 25% size model at 1/4 the speed, A = 0.094, v = 22.5, so
drag = 20N, power = 22.5m/s * 20N = 450W (< 1hp).
