External power supply for Otii Arc

Support
1

Can someone suggest a external power supply for Otii Arc? It must be 7.5-9V and 5A and have an EU mains plug.

2

We have seen issues with 5A AC adapters, creating noise in low power measurements.
For 5A supplies, I have used Volgen model KTPS45-0950DT-3P-VI but the measurement will be noisy in uA measurements.
The only low noise supply for 5A we have seen is the Extech 382260.

I can recommend the XP Power VEL18US090-EU-JA that we have used up to roughly 2.7A without problems.

Best regards,
Björn

3

We have ordered and tested with XP Power 9V 4A power adapter and it is much more noisy than using USB or laboratory power supply. Later I found your FAQ page “How do I select the right power supply” and it says that external power adapters with rating above 2A have been found be quite noisy. I wish I knew that.

  • for 0-4.2V and 0-200mA I will use USB
  • for 0-5V and 0-2.5A I will use our laboratory power supply

BTW you datasheet says max current is 250mA, while on the FAQ I read 200 mA, I think you need to update one of them

4

Hi,
sorry about the adapter. Working with low power you run into stuff that you otherwise don’t see or care about otherwise. We are collecting recommendations for above-2A power supplies, so please share any experiences, good and bad.
And thanks for spotting the typo, we’ll fix !
BR,
/Marc

5

Well that’s a bit of luck - I have two of those Extech 382260 supplies at home…

Do you have an input supply noise/ripple etc requirement needed to meet the published Otii spec?

Is the coupling mechanism affecting measurements known?

6

Hi Jared,

Input ripple for DC plug should be <10mV p-p for noise <1kHz

Best regards,
Björn

7

Cheers Bjorn!
I’ll print a couple of stickers for the back of the Otii’s we have here…

8

How does the Otii Arc know whether to use the internal or external power supply?

9

Hi Bruce,

If external power supply is connected and it is within 7-9V then the external power supply is used.

Best regards,
Björn

10

Thanks, that’s what I thought. I am working on an IOT device that has a LORA radio. When the radio transmit, it appears, the arc can not supply current(LORA transmit max ~120mA) fast enough. The voltage drops approximately 300-400mV at the start of the transmission. Is this something users have experienced while using the Otiis? Or do I have another problem?

11

Hi,

This is not normal behavior and I suspect the setup.
To dig deeper in this issue, I suggest that you create a case in our case system with information about your setup and attach a Otii project that shows this behavior.

Best regards,
Björn