Power consumption question

Hi there @squarpadmin !

Great work on the new module. It seems that powering the pyramid via the hermod would yield a combined current draw of 1320mA. Have you tested this on an intelljel stealth case loaded up with modules on the +/-12V rails (purported max of 5V rail on the 80watt TPS supply is 1500mA)? I’m curious if it would introduce any noise, or if power-on spikes are an issue…

Thank you for your work!

Hi @tehnir

  1. Are you talking about Hermod or Hermod+ ?
  2. How did you end up with 1350mA? It seems excessive. If we’re only talking about the +12V rail, it should stay well within 1000mA.
  3. Pyramid does not really draw 500mA, it’s just using a regular USB power supply, which specifies a nominal power capacity of 500mA. I don’t have exact numbers to give you, but it should be well below that.
  4. Hermod, particularly with a USB device plugged in, can introduce some noise into the power rail. Your mileage may vary, as it is really dependent on the overall system, other modules, the power supply, etc. Hermod+ has a much more refined power circuitry which greatly reduces this.
  5. USB devices can sometimes cause power-on spikes, yes. Pyramid should be pretty reasonable, and if we’re talking about Hermod+, its power circuitry also helps in that regard.

Let me know if I can be of any more help

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Hi @Thibault_Squarp - thank you for your reply. My replies inline below:

  1. Hermod+
  2. 500 + 820 (as of tonight), the number currently listed on modgrid
  3. ah I see; thank you for clarifying
  4. "
  5. awesome! ^___^

Ah, my bad, on the 5V rail, that is correct.
Using the Intellijel Stealth Case, you might want to stick with using the 12V rail, with has a much higher power budget.

@tehnir You might know the following, I’m just writing this for potential future readers:
For the record, Hermod+ has a switch, which sets the 5V power source. It can either be the 5V rail of the PSU, or using an internal power regulator which uses the +12V rail as input and outputs 5V.

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ah ok, so if I hook up the pyramid to the hermod+ as host with the power switched to +12V rail, does the extra amperage of the pyramid get drawn from the 5V supply of the case, or the generated 5V of the module? I apologize if this question is silly; I just hadn’t understood that modules can generate their own power sources.

Not at all!

If the power switch is set to use the +12V rail, the +5V rail won’t ever be used by the module. It might as well not even exist which is the case for some power supplies).

Long story short, the extra power required by Pyramid will be drawn from the +12V rail.
In this configuration, plugging a USB device into the HOST port of Hermod+ should only add up to an extra +200mA consumption on the +12V rail (that is, if the device is compliant with USB power specifications)

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okie! :slight_smile:
I will assume that pyramid mk3 will draw around 200mA and that it is compliant. Good to know this info for other devices I might consider.