When I look at the schematic of the Maple Rev5 it looks like it has 2 voltage regulators, one goes to VCC and one to VDDA (analog voltage). What is the curent rating on these, i.e how much current can the maple provide to other shields through the VCC and/or VDDA pins?
I didn't see a part number in the schematic (https://github.com/leaflabs/maple/blob/master/maple-r5/maple-r5-schematic.pdf).
Thanks,
Mike
Maple R5/RET6 - Voltage regulators
(10 posts) (4 voices)-
mikep
MemberPosted 4 years ago # -
robodude666
MemberThe technical specifications discuss this. Both regulators are capable of providing up to 250mA each.
If you look through documentation and see a claim that the Maple is capable of 800mA, please report it as this is an old figure from an earlier revision of the Maple. That regular part is no longer used due to limited supply.
Posted 4 years ago # -
gbulmer
Moderatormikep - there is some more discussion about the available power on this thread
http://forums.leaflabs.com/topic.php?id=768The calculation is a bit more involved than the current rating of the regulators.
Summary:
1. The current (theoretically available) by combining the two regulators is 500mA
2. The datasheet for the STM32F103 says it consumes 50mA at 72MHz with all peripherals enabled
3. The GP I/O pins can source or sink current up to a maximum of 150mA, depending on what you are doing with them
4. Linear voltage regulators reduce the voltage by converting power to heat. Those SOT-23 regulators can dissipate about 1/3rd Watt (more if there is plenty of copper there, and I haven't checked the PCB), but in the absence of significant area of copper on the PCB they only supply 250mA each when the input voltage is about 5V. At a higher voltage drop (input voltage to 3.3V) current is reduced.Edit:
5. If you join the two 250mA voltage regulators to provide a single, combined, 3.3V supply, then the noise on the analogue inputs will suffer.(full disclosure: I am not a member of LeafLabs staff)
Posted 4 years ago # -
robodude666
MemberWith all that said, you should strive to not be at the maximum that can be supplied. The Maple can supply at most 500mA with both regulators combined. That means you should try to at most use ~250 - 350mA (in my opinion, to be safe). The closer you are to the maximum rating the lower the efficiency of the regulators will be, which means more heat and wasted energy will be generated.
Posted 4 years ago # -
mikep
MemberThank you for all your input.
The reason I was asking is because I have an Ethernet Shield with ENC28J60 (http://www.thaieasyelec.net/index.php/Arduino/Ethernet-Arduino-Shield-ENC28J60/p_128.html) that I want to connect to the Maple (actually I have connected it, but I wanted to see if there is a better way). The shield draws about 130mA on it's 5V pin, and it has an onboard regulator since the ENC28J60 is also a 3.3V part. So I was thinking of just bridging the onboard regulator and feeding the shield from the maple regulator. Based on your statements that should be possible.
Right now I have the shield hooked up to the Vin pin of the Maple and I am powering the Maple through the MiniUSB port, so Vin has about 4.7V and the shield is working fine with that.
BTW, I got that Ethernet library to work (http://www.nuelectronics.com/estore/index.php?main_page=product_info&products_id=4), my Maple is on the Internet now ;).
Technically it should also work with the NuElectronics shield by bridging the voltage regulator, but I haven't tried that yet, it's tied up in another project.Posted 4 years ago # -
gbulmer
Moderatorrobodude666 -
The closer you are to the maximum rating the lower the efficiency of the regulators will be, which means more heat and wasted energy will be generated.
While intuitively attractive, can you point at something to substantiate that?
AFAIK the efficiency of any regulator is = Power-out / Power-in
I am curious to understand what changes to cause the loss of efficiency.Posted 4 years ago # -
gbulmer
Moderatormikep - Well done on getting the Ethernet library working. Were there many changes to make? Might you contribute the changes to the wiki?
I couldn't get to the server at http://www.thaieasyelec.net, so I am not sure if there is anything else on the shield, but
the datasheet for the ENC28J60
http://ww1.microchip.com/downloads/en/DeviceDoc/39662c.pdf
says it can consume a *maximum* of 180mA for transmitting a packet (page 80), so using power from the Maple should be okay. That could save up to 0.3W at 5V.(full disclosure: I am not a member of LeafLabs staff)
Posted 4 years ago # -
mikep
Membergbulmer -
the changes needed were mostly in the enc28j60 specific files, mainly the SPI routines and getting SPI to work. The rest is really dealing with the idiosyncracies of mixing C/C++ code and getting that to work with the MapleIDE compiler, since the library is basically based on the Tuxgrapgics TCP/IP stack ( http://www.tuxgraphics.org/electronics/200905/embedded-tcp-ip-stack.shtml ). I am going to set up a GitHub repo since I don't think there is a way to attach a zip file in the Wiki, but I definitely plan on sharing this.
PS: yes, their english server (thaieasyelec.net) seems to be down at the moment. The shield also has a MicroSD card on it and an SPI EEPROM, so you can switch between these 3 SPI devices using different CS pins. But I have only used the Ethernet portion so far. Also, this should theoretically work with any of the ENC28J60 adapters available on EBay.Posted 4 years ago # -
mikep
Member@TeunBende
I haven't really used the code in a while, but here it is.
Drop the library into the "libraries" folder of MapleIDE installation ("...\My Documents\MapleIDE\libraries" on Windows) and try to run the included PDE file.https://drive.google.com/file/d/0B1enDtNrhBu9a2FIbkFtRXBwUFk/edit?usp=sharing
https://drive.google.com/file/d/0B1enDtNrhBu9X0hBQXZ2aE5OSE0/edit?usp=sharingMake sure the ENC28J60 gets appropriate stable 3.3V power.
Good Luck,
MikePosted 1 year ago #
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