Hi,
I designed the qwiic quad relay into a project without realizing that the qwiic system (or at least this product) uses 3.3V for logic levels and Vcc (I had assumed 5V).
From a quick look at the schematic (https://cdn.sparkfun.com/assets/2/d/3/1 … _Relay.pdf) it seems that using 5V for SCL, SDA, and VCC should be fine, except maybe the currents into the optoisolator diodes might be a bit over spec.
Anyway, I wondering if I’m right, and driving things at 5V should work.
Thanks.
Hello, and thanks for your question!
We haven’t actually tested 5 volt I/O with this board.
Short term, 5 volt I2C would probably be OK, but for long term reliability of the ATtiny84 on the board, I’d recommend using a logic level converter like our [bi-directional logic level converter or the [PCA9306.](https://www.sparkfun.com/products/11955)](https://www.sparkfun.com/products/12009)
Terrific–thank so much for the quick reply.
I realized that another option is to just put a 3.3v regulator on the VCC line. Since I don’t have pullups on the SDA and SCL lines on my board. Presumably then things get pulled up to 3.3V in the relay board… I’ve got an AVR on my board, and according to the spec sheet, it should read anything above 3V as a HIGH level when powered at 5V.
Any thoughts on that option? (I don’t have too much experience with I2C)
Thanks
Hello! I’m the engineer that designed the Qwiic Quad Relay. I had to dig into my memory banks to remember which decisions I had made when I designed this board. The ATtiny on the Qwiic Quad Relay is 5V tolerant so you should be good there, and the reason you’re not seeing resistors on those lines is because I’m using the internal pullups on the ATtiny (10k). I believe the other components will be good at 5V as well, but make sure to monitor the heat around the board as you start turning on some relays.
As to your last post, dropping down to 3.3V before going into the Qwiic Quad Relay would also work. The digital signal would be 5V, but again those pins are 5V tolerant so should be fine.
Hey–thanks so much for your reply wonder_boom!
I’ve been testing things out at 5V (VCC and I/O) and only two of the 4 relays are working. I’ve measured the voltages on the current limiting resistors into the relays (r1, r12, etc) in the on-state and for both working and non-working relays the result is 3.1V, which would indicate about 58mA (1.9V/33Ω)through the relay coil.
Having trouble understanding what is going on after looking at the relay data sheet; 58mA is comfortably above the 38mA rated current, so I’d expect the relay to switch. However, the coil DC resistance is quoted at 330Ω, which would imply that there’s 19V across the coil when on… and that obviously isn’t happening.
Further, the “Pick-up Voltage” of the coil is listed as 9V, further confusing me.
Would be grateful for any insight you could share.
I’ve been testing things out at 5V (VCC and I/O) and only two of the 4 relays are working.
You’re going to need at least 7 volts at the barrel jack on the board for all four relays to function properly. The barrel jack only supplies power to the relays and the ATtiny gets it’s power from the 3.3 volt Qwiic header. (or the solder pads on the board.)
We're actually using the 5 volt coil version of the same relay in the datasheet. The linked datasheet has the 12 volt coil listed but the contacts are the same for both.Further, the “Pick-up Voltage” of the coil is listed as 9V, further confusing me.
To be clear, in the earlier discussion, I was referring to 5V VCC for signals coming over the qwiic connector (i.e. for the avr, etc).
That being said, I am powering from 5V at the barrel jack, but have shorted the jumper as described in the hookup guide https://learn.sparkfun.com/tutorials/qw … e-overview. I’m using a PSU with plenty of amperage at 5V; is there something I’ve misunderstood?
Regarding the relay, is there are a spec sheet for the 5V version? I see that they list the JZC-11F-05VDC as the relay version, but the specs are for the 12v version? If so, that’s pretty darn confusing, and IMO worse than not having any data sheet at all.
I am powering from 5V at the barrel jack, but have shorted the jumper as described in the hookup guide. I’m using a PSU with plenty of amperage at 5V; is there something I’ve misunderstood?
That should be working just fine. Can you only activate 2 relays at a time or just the same 2 relays? What happens if you reduce the VCC voltage to 3.3 volts? The only thing I can think of that might be happening is that running the ATtiny at 5 volts might be overloading it when more than 2 relays are activated at a time. The current limiting resistors used on the opto isolators were chosen with a VCC of 3.3 volts in mind and 5 volts might be drawing too much current from the ATtiny to activate more than 2 relays simultaneously.
Sadly, everywhere I have looked I only find the 12 volt version. It looks like the manufacturer of the relay only has the one version of the datasheet.Regarding the relay, is there are a spec sheet for the 5V version?
Sorry–I should have been more clear. I’m never trying to actuate more than one relay at a time. And of the 4, only 2 activate–though I can see the blue LED light for all channels, even the non-functional one.
Sounds like the best plan is to simply avoid trying to operate this board with Vcc/signals at 5V.
Thanks.