I'm reading the eoma spec at elinux and there is limited information regarding the power requirements. It states "*a maximum of 3.5 watts should be respected" and "**Type II Cards should not exceed an average of 3.5 watts power consumption" and "*must adjust accordingly and stick within the 4 watt heat dissipation budget".
Is there a minimum requirement for supply current that must be available to the cpu card from a housing/device/socket for compatibility with multiple cpu cards (3.5 or 4 watts)?
What is the A20 cpu card power consumption (average/peak)?
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On Tue, Aug 30, 2016 at 6:51 PM, Joseph Honold mozzwald@gmail.com wrote:
I'm reading the eoma spec at elinux and there is limited information regarding the power requirements. It states "a maximum of 3.5 watts should be respected" and "Type II Cards should not exceed an average of 3.5 watts power consumption" and "must adjust accordingly and stick within the 4 watt heat dissipation budget".
those are practical guidelines. if you want to do an EOMA68 module that requires 4 to 4.5 watts you should look at flooding it with thermal gel and sealing it. 3.5 to 4.0 watts you can get away with using the exact same graphite paper that's used in mobile phones.
Is there a minimum requirement for supply current that must be available to the cpu card from a housing/device/socket for compatibility with multiple cpu cards (3.5 or 4 watts)?
there is no minimum requirement. the maximum requirement is 1.0 A @ 5.0V. above that, housings are REQUIRED to CUT ALL POWER WITHOUT WARNING, for safety reasons.
What is the A20 cpu card power consumption (average/peak)?
peak is around 3.5 watts.
l.
On 08/30/2016 03:35 PM, Luke Kenneth Casson Leighton wrote:
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Tue, Aug 30, 2016 at 6:51 PM, Joseph Honold mozzwald@gmail.com wrote:
I'm reading the eoma spec at elinux and there is limited information regarding the power requirements. It states "a maximum of 3.5 watts should be respected" and "Type II Cards should not exceed an average of 3.5 watts power consumption" and "must adjust accordingly and stick within the 4 watt heat dissipation budget".
those are practical guidelines. if you want to do an EOMA68 module that requires 4 to 4.5 watts you should look at flooding it with thermal gel and sealing it. 3.5 to 4.0 watts you can get away with using the exact same graphite paper that's used in mobile phones.
Is there a minimum requirement for supply current that must be available to the cpu card from a housing/device/socket for compatibility with multiple cpu cards (3.5 or 4 watts)?
there is no minimum requirement. the maximum requirement is 1.0 A @ 5.0V. above that, housings are REQUIRED to CUT ALL POWER WITHOUT WARNING, for safety reasons.
Seems like there should be a minimum power requirement that all cpu cards and devices must meet. What happens if someone makes an ultra low power cpu card that peaks at 200mA and I design my device/housing to meet that 200mA but not higher and I try to plug the A20 card into it? It will be unstable or not work at all.
What is the A20 cpu card power consumption (average/peak)?
peak is around 3.5 watts.
So, the minimum requirement for the A20 cpu card is ~700mA peak?
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On Tue, Aug 30, 2016 at 10:39 PM, Joseph Honold mozzwald@gmail.com wrote:
Seems like there should be a minimum power requirement that all cpu cards and devices must meet.
okay - so you used the word "devices" which is not part of EOMA68 terminology. sorry i missed this, so didn't understand the question.
*from the perspective of the EOMA68 Cards* the *MAXIMUM* that they are permitted to use is 1.0A @ 5.0v
therefore...
*from the perspective of EOMA68 ***HOUSINGS*** .... * the *MINIMUM* that they must provide is: 1.0A @ 5.0v
above exactly 1.0A @ 5.0v, housings are ***REQUIRED*** to cut power without warning.
What happens if someone makes an ultra low power cpu card that peaks at 200mA and I design my device/housing to meet that 200mA but not higher and I try to plug the A20 card into it? It will be unstable or not work at all.
okay now you're using the word "housing" so it's clear.
if you do not provide up to 1.0A that will not be compliant with the EOMA68 standard. you will risk having electronics burned out and possibly causing a fire hazard, potentially causing serious injury, destruction of property or death.
please don't do that. please make sure that you comply with the standard - make sure that the Housing provides up to the required 1.0A @ 5.0V and has the required "over-current" protection.
you can use something like a SY6280 or similar IC which provides over-current, short-circuit protection and over-temperature protection. the datasheet says that the SY6280 also discharges the output capacitor during shutdown, which is quite important.
What is the A20 cpu card power consumption (average/peak)?
peak is around 3.5 watts.
So, the minimum requirement for the A20 cpu card is ~700mA peak?
about that, yeah. but please do not rely on that as a design guide for selection of components. please ensure that you select the correct IC which covers all eventualities.
l.
On 30/08/16 23:11, Luke Kenneth Casson Leighton wrote:
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On Tue, Aug 30, 2016 at 10:39 PM, Joseph Honoldmozzwald@gmail.com wrote:
Seems like there should be a minimum power requirement that all cpu cards and devices must meet.
okay - so you used the word "devices" which is not part of EOMA68 terminology. sorry i missed this, so didn't understand the question.
*from the perspective of the EOMA68 Cards* the *MAXIMUM* that they are permitted to use is 1.0A @ 5.0v
therefore...
*from the perspective of EOMA68 ***HOUSINGS*** .... * the *MINIMUM* that they must provide is: 1.0A @ 5.0v
above exactly 1.0A @ 5.0v, housings are ***REQUIRED*** to cut power without warning.
This seems like a broken spec to me. Nothing in electronics is exact, so a sane spec should have a reasonable margin between the maximum current a card is allowed to draw and the point at which overcurrent protection is required to kick in.
--- crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Tue, Aug 30, 2016 at 11:35 PM, peter green plugwash@p10link.net wrote:
above exactly 1.0A @ 5.0v, housings are ***REQUIRED*** to cut power without warning.
This seems like a broken spec to me. Nothing in electronics is exact, so a sane spec should have a reasonable margin between the maximum current a card is allowed to draw and the point at which overcurrent protection is required to kick in.
appreciated - very good point this is the first time it's really been discussed. i'm already uncomfortable with the idea of having 5.0 watts in an enclosed space. 3.5 is okay. i _was_ thinking of raising the Housing limit to 5.5 watts, but was slightly concerned that people would abuse the extra headroom.
suggestions appreciated.... hmm... let me just add a section on the specification / discussion on the elinux.org talk page to reference this discussion...
l.
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On Tue, Aug 30, 2016 at 11:46 PM, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
suggestions appreciated.... hmm... let me just add a section on the specification / discussion on the elinux.org talk page to reference this discussion...
c/f purposes: http://elinux.org/Talk:Embedded_Open_Modular_Architecture/EOMA-68#Power_Prov...
On 08/30/2016 05:11 PM, Luke Kenneth Casson Leighton wrote:
Seems like there should be a minimum power requirement that all cpu cards and devices must meet.
okay - so you used the word "devices" which is not part of EOMA68 terminology. sorry i missed this, so didn't understand the question.
I spose motherboard is the correct term i should have used.
*from the perspective of the EOMA68 Cards* the *MAXIMUM* that they are permitted to use is 1.0A @ 5.0v
therefore...
*from the perspective of EOMA68 ***HOUSINGS*** .... * the *MINIMUM* that they must provide is: 1.0A @ 5.0v
Maybe I'm misreading the spec, but I don't see it specify that my motherboard must be able provide 5V 1A to the cpu card. That's the reason for asking this question.
above exactly 1.0A @ 5.0v, housings are ***REQUIRED*** to cut power without warning.
I don't see this in the spec either. Am I correct that http://elinux.org/Embedded_Open_Modular_Architecture/EOMA-68 is the 'official' specification for eoma-68? Or is there some other document?
This seems like a broken spec to me. Nothing in electronics is exact, so a sane spec should have a reasonable margin between the maximum current a card is allowed to draw and the point at which overcurrent protection is required to kick in.
appreciated - very good point this is the first time it's really been discussed. i'm already uncomfortable with the idea of having 5.0 watts in an enclosed space. 3.5 is okay. i _was_ thinking of raising the Housing limit to 5.5 watts, but was slightly concerned that people would abuse the extra headroom.
suggestions appreciated.... hmm... let me just add a section on the specification / discussion on the elinux.org talk page to reference this discussion...
Adding a section for power specifics would help clarify things.
--- crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Wed, Aug 31, 2016 at 12:28 AM, Joseph Honold mozzwald@gmail.com wrote:
On 08/30/2016 05:11 PM, Luke Kenneth Casson Leighton wrote:
Seems like there should be a minimum power requirement that all cpu cards and devices must meet.
okay - so you used the word "devices" which is not part of EOMA68 terminology. sorry i missed this, so didn't understand the question.
I spose motherboard is the correct term i should have used.
"Housing" is now the official term. motherboard usually means "CPU is on.... the motherboard".
*from the perspective of the EOMA68 Cards* the *MAXIMUM* that they are permitted to use is 1.0A @ 5.0v
therefore...
*from the perspective of EOMA68 ***HOUSINGS*** .... * the *MINIMUM* that they must provide is: 1.0A @ 5.0v
Maybe I'm misreading the spec, but I don't see it specify that my motherboard must be able provide 5V 1A to the cpu card. That's the reason for asking this question.
i know... and it's a good question, which is why i've started a section on the discussion page.
above exactly 1.0A @ 5.0v, housings are ***REQUIRED*** to cut power without warning.
I don't see this in the spec either. Am I correct that http://elinux.org/Embedded_Open_Modular_Architecture/EOMA-68 is the 'official' specification for eoma-68?
yes. so it needs to be on that.
This seems like a broken spec to me. Nothing in electronics is exact, so a sane spec should have a reasonable margin between the maximum current a card is allowed to draw and the point at which overcurrent protection is required to kick in.
appreciated - very good point this is the first time it's really been discussed. i'm already uncomfortable with the idea of having 5.0 watts in an enclosed space. 3.5 is okay. i _was_ thinking of raising the Housing limit to 5.5 watts, but was slightly concerned that people would abuse the extra headroom.
suggestions appreciated.... hmm... let me just add a section on the specification / discussion on the elinux.org talk page to reference this discussion...
Adding a section for power specifics would help clarify things.
yeahyeah.
l.
...if I may, why "housing" and not "dock"...? I know I've been kind of half-heartedly pushing "dock" for a while now... but it's a shoe that fits, you know?
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On Wed, Aug 31, 2016 at 3:08 AM, Christopher Havel laserhawk64@gmail.com wrote:
...if I may, why "housing" and not "dock"...? I know I've been kind of half-heartedly pushing "dock" for a while now... but it's a shoe that fits, you know?
"dock" (or "docking station") is already in public use, as is "lapdock". as in "docking station" for a laptop (which used to be common up until 10 years ago) and "motorola atrix lapdock".
l.
On 31/08/16 03:32, Christopher Havel wrote:
On 31/08/16 03:31, Luke Kenneth Casson Leighton wrote:
On Wed, Aug 31, 2016 at 3:08 AM, Christopher Havel laserhawk64@gmail.com wrote:
...if I may, why "housing" and not "dock"...? I know I've been kind of half-heartedly pushing "dock" for a while now... but it's a shoe that fits, you know?
"dock" (or "docking station") is already in public use, as is "lapdock". as in "docking station" for a laptop (which used to be common up until 10 years ago) and "motorola atrix lapdock".
...that sounds like a plus, to me...
I think Luke's point is that an EOMA68 computing card (optionally) plugs into a housing, which could then in turn (optionally) plug into a dock.
So, it is useful to have the three different terms, and for them to have distinct meanings, as above.
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