Looks good! A couple comments/observations: 1. I'd skip the SD card. We have lost so many of them on orbit, we have given up using them. Never used MRAM on orbit, but I've heard good things. We usually go with FRAM. 2. I'm not sure how accurate of a sun sensor you need, but you may be able to get away with using the power output from each solar panel (if they aren't tied together). We did this on one cubesat we launched when I was in grad school and had ok results. 3. Don't worry too much about the crazy temperature ratings. At the end of the day, your batteries are by far the most temperature sensitive component you will have on your spacecraft. So don't fret too much about it. Additionally, from the variety of spacecraft I've been involved with, you really only start to have temperature issues when you get into bigger cubesats. Even 3U's are pretty easy going with respect to temperature. 4. The off chip watchdog is invaluable. I'd recommend that circuit be able to power cycle as much of the spacecraft as possible. SEUs are gonna happen, it's important to plan for a strategy to deal with them.
Hey Nick! Thanks for the feedback. 1) The SD card is starting to sound like more trouble than it is worth. It's just a convenient & cheap interface to bulk storage. Have you had any experience with eMMC storage? Not that I have any storage requirements at the moment, I just like having the ability. 2) Right. And it's not like I _need_ super accurate sun sensing right now, Im more interested in finding a cheap way of accomplishing it. 3) Makes sense! 4) I'll try to incorporate that! On the topic, I get stuck thinking about "who watchdogs the watchdog". Since nothing on this board is rad hard, everything could experience SEUs or SELs. What if the watchdog fails and permanently holds the MCU in reset? What if my current-monitoring circuit latches up? Are these things I should worry about?
@@RGSAT I've had less on orbit experience with soldered on eMMC, but the single data point I have had similar behavior to an SD card. As for RAD hard components, the majority of the spacecraft I have launched have not had any RAD hard components. There is indeed some risk to having a single point of failure, and usually you just have to hope your watchdog circuit is going to be robust enough. If it is simple enough, you'd be more likely to see the watchdog occasionally trip when it shouldn't instead of it hanging partway through a reset (and keeping your MCU in reset). As for your power monitoring circuitry, if possible, I'd put that under your watchdog's control as well. Normally, you would use a sort of hierarchical watchdog system and have software on your flight computer that can power cycle things automatically if they aren't responding or giving bad data. This sort of thing is usually called FDIR, if you want to read more about it.
That actually gives huge relief on the whole, well explained tho some btw can u pls send this Schematic diagram of CubeSAT avionics board for Electrical Reference buddy!
Your TCXO could be GPS-locked since your including a gps chip which BTW a usb gps chip on board is available from amazon for $6. Your temp sensors could double as sun sensors espically if you use the solar cells for redundancy.
because of bitflipping planes use blockchain style tech so redundencies and positioning are something you might need in a cube sat maybe design a board, if you make this a manufacturing idea design 2 boards that interlock with a cut in their middle so they become a cross and the middle part can be a connector Water based microsatelite propultion is currently being tested using energy from ambient radiation to create steam out of ice as for the solar panels you could stick the antena in one of the edges, on one of the edges so that it covers more 2 dimentional surface area relative to the sun
1. Blockchain works by spreading the data across nodes and then run a majority vote on the data. So writing some data into 3 locations in memory and ignoring a bit flipped version may be a good idea. It requires 3 times more memory. Simplest Hamming code (4 bits of data on 7 bits of memory) is more efficient. 2. Cool idea for solar-thermal propulsion
In such a small form factor it is difficult to have true radiation shielding, and radiation hardened components are quite expensive. The best I can do is have several levels of watchdogs to reset my system in the case of radiation flipping-bits, and monitor current to prevent the damaging effects of latch-ups. See my EPS videos for more discussion on Current Monitoring!
@@RGSATIf it's going to be helpful 4 years later... If your satellite can be made a bit heavier and doesn't exceed the limit, you can add shielding made of aluminum plates. Or use an aluminum-backed PCB for a part of the circuit - like the ones used for LEDs - so it's both a PCB and a shield. Just my idea, I never actually built something like that before ;)
I was thinking of using the MLX75306, but I'm not sure. It isn't very cheap, and I think it is obsolete. I'm currently re-thinking what sort of sun sensor I could design.
Looks good! A couple comments/observations:
1. I'd skip the SD card. We have lost so many of them on orbit, we have given up using them. Never used MRAM on orbit, but I've heard good things. We usually go with FRAM.
2. I'm not sure how accurate of a sun sensor you need, but you may be able to get away with using the power output from each solar panel (if they aren't tied together). We did this on one cubesat we launched when I was in grad school and had ok results.
3. Don't worry too much about the crazy temperature ratings. At the end of the day, your batteries are by far the most temperature sensitive component you will have on your spacecraft. So don't fret too much about it. Additionally, from the variety of spacecraft I've been involved with, you really only start to have temperature issues when you get into bigger cubesats. Even 3U's are pretty easy going with respect to temperature.
4. The off chip watchdog is invaluable. I'd recommend that circuit be able to power cycle as much of the spacecraft as possible. SEUs are gonna happen, it's important to plan for a strategy to deal with them.
Hey Nick! Thanks for the feedback.
1) The SD card is starting to sound like more trouble than it is worth. It's just a convenient & cheap interface to bulk storage. Have you had any experience with eMMC storage? Not that I have any storage requirements at the moment, I just like having the ability.
2) Right. And it's not like I _need_ super accurate sun sensing right now, Im more interested in finding a cheap way of accomplishing it.
3) Makes sense!
4) I'll try to incorporate that! On the topic, I get stuck thinking about "who watchdogs the watchdog". Since nothing on this board is rad hard, everything could experience SEUs or SELs. What if the watchdog fails and permanently holds the MCU in reset? What if my current-monitoring circuit latches up? Are these things I should worry about?
@@RGSAT I've had less on orbit experience with soldered on eMMC, but the single data point I have had similar behavior to an SD card.
As for RAD hard components, the majority of the spacecraft I have launched have not had any RAD hard components. There is indeed some risk to having a single point of failure, and usually you just have to hope your watchdog circuit is going to be robust enough. If it is simple enough, you'd be more likely to see the watchdog occasionally trip when it shouldn't instead of it hanging partway through a reset (and keeping your MCU in reset).
As for your power monitoring circuitry, if possible, I'd put that under your watchdog's control as well.
Normally, you would use a sort of hierarchical watchdog system and have software on your flight computer that can power cycle things automatically if they aren't responding or giving bad data. This sort of thing is usually called FDIR, if you want to read more about it.
Please can I get this project pdf files from you mentor?
This is such an amazing series.
Thanks a lot for this series, and for the excellent explanation
That actually gives huge relief on the whole, well explained tho some btw can u pls send this Schematic diagram of CubeSAT avionics board for Electrical Reference buddy!
For the radio think about a LoRa module $5 for ground station R-PI 0 +Lora RFM 96 and omni antenna 3/4 wave length will close the link
Thanks! I need to look into it
I really enjoy your videos but we have launch 3 1 U cubes and the internal temps are -10 to 30 C mostly 5 C . Reconsider the LoRa radio
Your TCXO could be GPS-locked since your including a gps chip which BTW a usb gps chip on board is available from amazon for $6. Your temp sensors could double as sun sensors espically if you use the solar cells for redundancy.
Nice Video Bud! Why you are not consider using IMUs instead of expensive gyros accelerometers etc?
Hi there can u plz share the gerber file of the schematics of the pcb, it will be really appreciated
because of bitflipping planes use blockchain style tech so redundencies and positioning are something you might need in a cube sat
maybe design a board, if you make this a manufacturing idea
design 2 boards that interlock with a cut in their middle so they become a cross and the middle part can be a connector
Water based microsatelite propultion is currently being tested using energy from ambient radiation to create steam out of ice
as for the solar panels you could stick the antena in one of the edges, on one of the edges so that it covers more 2 dimentional surface area relative to the sun
1. Blockchain works by spreading the data across nodes and then run a majority vote on the data. So writing some data into 3 locations in memory and ignoring a bit flipped version may be a good idea. It requires 3 times more memory. Simplest Hamming code (4 bits of data on 7 bits of memory) is more efficient.
2. Cool idea for solar-thermal propulsion
I made a CubeSat in CAD. You can have it fro free to download its 10cm x 10cm x 10cm
very decent of you.
I notice you are specking parts -40 to + 125 d eg C my experience in flying 3 1 U cubes the temperature range -s -5 to + 30 deg C ?
I'm spec-ing parts with those ranges just to be safe! I know for LEO temperature isn't a huge deal.
Crazy wow
Hi dude!
When is the next video!!
Should be tonight!
@@RGSAT waiting dude...
What is the time period of this project?? Waiting for the final video...
@@velkadamban I'm working on it whenever I have time, but it might be a little while before this thing is fully complete!
What about radiation protection?
In such a small form factor it is difficult to have true radiation shielding, and radiation hardened components are quite expensive.
The best I can do is have several levels of watchdogs to reset my system in the case of radiation flipping-bits, and monitor current to prevent the damaging effects of latch-ups.
See my EPS videos for more discussion on Current Monitoring!
@@RGSATIf it's going to be helpful 4 years later...
If your satellite can be made a bit heavier and doesn't exceed the limit, you can add shielding made of aluminum plates.
Or use an aluminum-backed PCB for a part of the circuit - like the ones used for LEDs - so it's both a PCB and a shield.
Just my idea, I never actually built something like that before ;)
What is the sun sensor part #?
I was thinking of using the MLX75306, but I'm not sure. It isn't very cheap, and I think it is obsolete. I'm currently re-thinking what sort of sun sensor I could design.
Hey. How can I get a copy of that schematic? TIA
Have at it: raw.githubusercontent.com/rgw3d/1KCubeSat_Hardware/master/avionics_board/output_04_24.pdf
Can you give diagram
Hi. How can I contact you?