PZEM-017 only works with external supply

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Khurram

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Dec 3, 2021, 11:12:20 AM12/3/21
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I have a pzem-017 which is connected to a 5V dc power supply through its RS-485 block. I am not able to get reading from it unless I also connect an external 5V supply to its micro-usb port. I have confirmed that it is receiving 5V on its RS-485 block. I have also confirmed that the sense voltage is > 5V. The pzem is supposed to sense voltage+current from two 12V solar panels connected in parallel. Is this piece faulty?

Thanks
Khurram

Philip Knowles

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Dec 3, 2021, 12:24:40 PM12/3/21
to Khurram, TasmotaUsers

This isn’t a Tasmota issue but the voltage at the sense terminals needs to be above 7V not 5V. It’s states that both in the manual and the back of the device. The RS485 input is isolated from the sense circuit.

 

Regards

 

Phil K

 

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Khurram

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Dec 3, 2021, 12:39:30 PM12/3/21
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During the day, the voltage was about 14V but the pzem was not detected. Once I connected the 5V supply to the micro-usb port, it was detected and I got the readings.

You are right its not a tasmota issue. Since I am using it with a tasmotized nodemcu, I thought I would post it here. I will not make further posts here on this issue if it is not allowed.

Philip Knowles

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Dec 3, 2021, 1:20:54 PM12/3/21
to Khurram, TasmotaUsers

It’s fine but sometimes we can end up with side discussions.

Presumably you have some form of charge controller as the load.

The PZEM shunt should be connected between the -ve of the charge controller and the -ve of the solar panel. Hopefully, you’ve connected like this.

Khurram

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Dec 3, 2021, 2:26:23 PM12/3/21
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I am afraid you lost me here. I have connected the pzem sensor side as follows.

MainEnclosure2.png

Is this the same as in your post? I have measured the voltage on points 1 and 2 during the day and it was about 14V. Even then, I could not get any readings from the pzem.

Thanks

Philip Knowles

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Dec 3, 2021, 3:38:09 PM12/3/21
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Looks the same (you said that you had 2 in parallel which is why mine looks more complicated)..

Do you get a current reading too or just the voltage?

 

The fact that you get a reading when connected to the USB connection sounds like there isn’t a fault with the device.

 

Regards

 

Phil K

 

 

Sent from Mail for Windows

 

From: Khurram
Sent: 03 December 2021 19:26
To: TasmotaUsers
Subject: Re: PZEM-017 only works with external supply

 

I am afraid you lost me here. I have connected the pzem sensor side as follows.

 

Khurram

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Dec 4, 2021, 8:40:31 AM12/4/21
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Yes I have 2 pzems; one for sp and one for load measurement. The load pzem works fine; the sp pzem does not. I have found that even with the usb power connected, the sp pzem only works intermittently. So it is not a power issue. I connected the sp pzem to an rs485-usb converter, connected it to my laptop over usb and tried to access the various registers through QModBus; it still worked intermittently. So  maybe it is a faulty pzem. I have ordered another one and have to wait for about 2 months for it to get here.

Thanks.

Philip Knowles

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Dec 4, 2021, 1:21:03 PM12/4/21
to Khurram, TasmotaUsers

Have you changed the address of the PZEM or are you using separate devices to read each? There is a PeaceFair Windows app which should connect to the device (and let you change the module address etc)

 

Phil K

 

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From: Khurram
Sent: 04 December 2021 13:40
To: TasmotaUsers
Subject: Re: PZEM-017 only works with external supply

 

Yes I have 2 pzems; one for sp and one for load measurement. The load pzem works fine; the sp pzem does not. I have found that even with the usb power connected, the sp pzem only works intermittently. So it is not a power issue. I connected the sp pzem to an rs485-usb converter, connected it to my laptop over usb and tried to access the various registers through QModBus; it still worked intermittently. So  maybe it is a faulty pzem. I have ordered another one and have to wait for about 2 months for it to get here.

 

Thanks.

 

On Saturday, 4 December 2021 at 01:38:09 UTC+5 knowles...@gmail.com wrote:

Looks the same (you said that you had 2 in parallel which is why mine looks more complicated)..

Do you get a current reading too or just the voltage?

 

The fact that you get a reading when connected to the USB connection sounds like there isn’t a fault with the device.

 

Regards

 

Phil K

 

 

Sent from Mail for Windows

 

From: Khurram
Sent: 03 December 2021 19:26
To: TasmotaUsers
Subject: Re: PZEM-017 only works with external supply

 

I am afraid you lost me here. I have connected the pzem sensor side as follows.

 

 

Is this the same as in your post? I have measured the voltage on points 1 and 2 during the day and it was about 14V. Even then, I could not get any readings from the pzem.

Khurram

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Dec 4, 2021, 1:29:57 PM12/4/21
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I use 1 RS485 adapter. I used QModBus to change the sp pzem address to 2 (the load pzem is at 1).

Thanks

Philip Knowles

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Dec 4, 2021, 1:31:43 PM12/4/21
to Khurram, TasmotaUsers

OK. It may be worth trying swapping the addresses to see whether it’s a Tasmota issue on the comms side.

Khurram

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Dec 5, 2021, 8:39:54 AM12/5/21
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This is really strange. This morning the load pzem just started working. I did not change anything. The readings stopped after sunset but that is expected. I will see tomorrow if it starts working again.

I don't think changing the address will change anything as I cannot get this pzem to work reliably when connected directly to QModBus using an RS485-TTL adapter.

Thanks.

Khurram

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Dec 5, 2021, 9:01:10 AM12/5/21
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In the above post, I meant the sp pzem (not the load pzem). Sorry for the typo.

Khurram.

Philip Knowles

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Dec 5, 2021, 9:13:38 AM12/5/21
to Khurram, TasmotaUsers

To get mine to work reliably I switch in a USB supply when the voltage drops below 8V

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Khurram

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Dec 5, 2021, 11:23:03 AM12/5/21
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Yes I would be connecting the sp pzem to the usb supply once I get the isolated dc supply from Ali Express as advised by you.

Thanks
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