WR21 Brownout Recovery

Question

When the input dc power on a WR21 drops below the operational limit, the unit browns out and appears not to recover when the input dc power goes above the minimum operational limit (I have taken it to 24V input). After completely powering off it recovers and becomes operational. Is this normal behavior?

Any suggestions for changing this behavior would be appreciated.

Answer 1

Hi

if the router brownout then it can get into a stuck state and would have to have the power removed fully before the router works correctly

as the router is rated with input voltage and if this is not followed then this type of issue will occur

the best way forward would be to provide the correct power level and protect for voltage drop like this

https://www.amazon.co.uk/12v-Battery-Discharge-Protector-Guard-Black/dp/B004AUJ002

regards

James

Answer 2

Just to add to James' post. What voltage and for how long are you seeing this that causes the device to lock up?

This is not "normal" but if the input is out of spec then you will have unknown behaviour and should correct the power but I assume this is caused by a generator or something so if you cannot correct the power then you should install a low voltage cut off.

Most battery isolators have a timer to allow for fluctuations in power. In your case you would want an isolator that cuts out immediately if you can find one.

Alternatively ask your electrician to install an under voltage monitoring relay. This will cut out immediately (normally within 0.1-0.5 seconds) when the 24VDC drops below a certain point. You can get them from Phoenix Contact, Eaton etc.

Here is an example of one: http://uk.rs-online.com/web/p/monitoring-relays/7300509/

This has a Drop-out voltage of >30% of minimum rated supply voltage, which is 24VDC so it would cut off at 16.8VDC.

Obviously the WR21 is rated from 9-36VDC so the device would be protected from under voltage and restart once the power returns to a normal voltage.

Answer 3

Thanks James and Nicholas. I am actually going to handle this in software as I already have a way to control power in my circuitry. I asked the question just because I want to make sure it was normal behavior, even though I have seen it on multiple units. I am surprized that Digi did not include brownout protection in the device as it is standard practive in good electrical design.