reef-pi :: An opensource reef tank controller based on Raspberry Pi.

[buddy.]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

 

[LionHeart2017]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

You might be better to share some pictures of it

 

[ScottBrew]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

How are the chips oriented in regards to the notch at one end of each chip? The com and ground are at the opposite end from the notch.

 

[ScottBrew]

Thanks. I will give it a try. I am not too familiar with macros

A macro is just a series of commands, in whatever order you set them up. Use mine for a template if you like. Just remember to turn off the corresponding timer controlling any device. For instance, my powerheads are set to time intervals that could make them run while in feeding mode if the timer went off. So, timer off for each powerhead, then the powerhead itself. Hope that is clear.

 

[buddy.]

You might be better to share some pictures of it

How are the chips oriented in regards to the notch at one end of each chip? The com and ground are at the opposite end from the notch.

Thanks for the replies, I have attached a picture of the pi-hat stacked on the raspberry. I can confirm that all of the chips are in the correct way.

 

[speedstar]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

You tested for continuity, but did you also test for shorts between pins. remove the chip and make sure no pin to pin traces are connected. Did you use sockets or chip direct to board?

 

[speedstar]

Sometimes solder blobs can get under the socket, apologies for not knowing your solder skills or electronics

 

[dmolavi]

I'm interested in the range of the dimmer input. e.g., is it 0-10V? 0-12V? 0-5V? etc. By measuring across the two fixed terminals in the potentiometer we know the full range of the dimmer input.

0-10V nominal.

There is a model of the Ranco that has an analog output for the temp reading (of course, I didn't get that one *facepalm*), but I'm guessing that it can be pulled from something on the PCB in the enclosure...

 

[Ranjib]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

How you are connecting the ULN2803 output to relays? Remember, ULN2803 is a sink type driver, i.e. individual output pins of ULN2803 will act as GND (not +ve) for relays. So, while testing with multimeter, you should put the +Ve probe on 12V and the -Ve probe in ULN2803a pins.

 

[buddy.]

You tested for continuity, but did you also test for shorts between pins. remove the chip and make sure no pin to pin traces are connected. Did you use sockets or chip direct to board?

Sometimes solder blobs can get under the socket, apologies for not knowing your solder skills or electronics

Thanks. I used a socket. I didn't test for shorts but I will do it tonight.

How you are connecting the ULN2803 output to relays? Remember, ULN2803 is a sink type driver, i.e. individual output pins of ULN2803 will act as GND (not +ve) for relays. So, while testing with multimeter, you should put the +Ve probe on 12V and the -Ve probe in ULN2803a pins.

The ULN output goes to the 10 pin connector on the pi-hat. So you have 1 5v, 1 ground and then 8 outlets.
I connected the 10pin connector 5v to the VCC on the relay board.
I connected the 10 pin ground to ground on the relay board.
I connected an outlet on the 10 pin to CH1 on the relay board.
When I have the outlet switched off in reef-pi the ULN output reads 0v and when I switch the outlet on the ULN output reads 0.6v. But I was putting the -ve probe to ground and the +ve on the ULN output.

 

[Diamond1]

Thanks. I used a socket. I didn't test for shorts but I will do it tonight.



The ULN output goes to the 10 pin connector on the pi-hat. So you have 1 5v, 1 ground and then 8 outlets.
I connected the 10pin connector 5v to the VCC on the relay board.
I connected the 10 pin ground to ground on the relay board.
I connected an outlet on the 10 pin to CH1 on the relay board.
When I have the outlet switched off in reef-pi the ULN output reads 0v and when I switch the outlet on the ULN output reads 0.6v. But I was putting the -ve probe to ground and the +ve on the ULN output.

Might be a stupid question but do you have a 12volt power supply hooked up to the hat when your testing?

 

[buddy.]

Might be a stupid question but do you have a 12volt power supply hooked up to the hat when your testing?

Yep I did but I haven't actually tested it. I thought it was only needed for the dosing pumps though?

 

[speedstar]

Yep I did but I haven't actually tested it. I thought it was only needed for the dosing pumps though?

correct

also wanted to mention the outputs on/off will be the inverse going through the chip compared to the pi direct.

 

[b4tn]

I posted this in my build thread but I am just going to post it here for more visibility.

I am testing out my 8 channel 5v relay boards.

First I tested with just the raspberry pi by connecting up the 5v, ground and an outlet GPIO and it worked as expected.

Next I tried with the pi-HAT but it is not activating the relay. The input of the ULN2803 is receiving 3.25v. The ULN2803 is outputting only 0.6v to the relay board.
I tried a different GPIO on the second ULN2803 on the pi-HAT with the exact same result.

The VCC light is on when I connect the relay board to the 5v and GND on the 10pin connector on the pi-HAT.

The ULN inputs have continuity with the GPIO outlets. The ULN outlets also have continuity with the 10pin connector.
The ULN's are also grounded on their number 9 pin and have 5v on their number 10 pin. Measuring the voltage on pin 9 and 10 gives 5v.

Can anyone help me figure out why the ULN2803 output is so low and not activating the relay?

I did the same thing. The output straight off the gpio pin is going to be 3.3 volts when on. But when you put the output through the ULN2803 the bias is reversed. The output is triggered to ground. To test with the volt meter put the ground probe on the 2803 output pin and the positive probe on the 12 volt rail. You should now see 12 volts when on. And nothing when off. Your relays will need to be set to low level trigger.

 

[Diamond1]

Like I said stupid question.

So what 12v is @Ranjib talking about to use for testing.

 

[speedstar]

Like I said stupid question.

So what 12v is @Ranjib talking about to use for testing.

The american DJ board power strip may use 12v relays instead of 5V

 

[b4tn]

You could Put the red positive test probe on the 12 volt pin of the 2803 and the ground probe on whatever output pin you are testing.

 

[b4tn]

The american DJ board power strip may use 12v relays instead of 5V

Missed that.

 

[buddy.]

I did the same thing. The output straight off the gpio pin is going to be 3.3 volts when on. But when you put the output through the ULN2803 the bias is reversed. The output is triggered to ground. To test with the volt meter put the ground probe on the 2803 output pin and the positive probe on the 12 volt rail. You should now see 12 volts when on. And nothing when off. Your relays will need to be set to low level trigger.

How to I set the relays to low level trigger?

 

[b4tn]

Do you have a link or a pic of the relays? Mine had jumpers