![]() There will also be some voltage drop across the inductor (probably 0.1V or less) and some across the transistor which switches the relay. more than one relay turned on), forward voltage could be as much as 1.25V typical, so maybe 1.4V or so maximum.Ĥ. The 1N4148 data sheet gives a maximum forward voltage drop of 1.0V at 100mA. (And I can imagine that some variants of the 1N4148 don't match that spec).ģ. So with more than two relays turned on at once, it's running beyond its limits. According to the 1N4148 data I found, maximum forward current is 300mA. There is a 1N4148 and an inductor in series with the incoming +5V supply the diode is probably to protect against reversed supply connections. The relay takes 120mA coil current at 5V, and requires a minimum of 3.75V to turn on (based on my non-existent Chinese).Ģ. Interesting to look at that circuit it has the potential to cause as many problems as it solves!ġ. I will leave you to decide what you consider to be the safer / better option.īoard (smugly suggested by ltolledo as being "specifically designed and made for use with the RPi boards"): I prefer to use / suggest what I consider is the safer option the use of external interface circuits, to my knowledge I have never had anyone post here saying one of my interface circuits destroyed thier pi and there have been some users that assembled them wrong. ![]() We could argue this till we are blue in the face, and still never agree. This is precisely what you get when you remove the VCC-JDVCC jumper! And connect relay power to JD-VCC and 3.3V to VCC! It's identical!īut its not as you don't have to remove any jumpers and start adding 3.3V supply to a 5V board its already been done and tested. Thank you for posting the diagram that disproved what you claimed. So it not exactly the same as the other boards as you claimed. So I missed the diagram but it does prove exactly what I said the standard 5V relay board design has been modified, so the opto isolators are in fact driven off the 3.3V and not the 5V. It would be more useful to explain how to connect them, and why their operation is marginal for some batches (and how to get around that). ![]() These relay boards work when configured and connected properly. Plus it adds another level of complexity. If you have little or no electrical knowledge then consider getting local physical help from someone that does, or use the simpler often used options, which often means leaving existing PCB unchanged and using external interfacing circuits to protect the pi.Īs one user found recently diving straight in with no electrical experience can result in the destruction of a pi.īuilding an external circuit does not necessarily protect anything if a user builds it wrong or connects it wrongly. So before following any instructions make sure you understand what is required and that you are confident that you can perform the required actions / modifications in a safe way, if you have any doubts don't do it. So when following information provided on these forums take in to consideration you own skill level, may users here who offer help have years of electrical /electronics experience. One point I would like to make and this is not aimed at any specific user that is trying to help or any user following instructions. ![]() The relay board's 5V (on JD-VCC) is still recommended to be powered separately from the RPi then its time to integrate it to the RPi's GPIO. Once all are confirmed working on this setup. Looks like pcmanbob already posted it above Look for the famous diagrams of pcmanbob (yes. it is recommended to use a ULN2803AN (or its equivalanets), as it already have built in base resistors on each transistor, which makes wiring much easier. If your relay does not make a *click* sound on either (5) or (6), then you need an additional transistor circuit (which makes the whole setup as active high)įor an 8-channel relay. remove the Gnd wire to IN1, (and connect 3.3v) does the relay on IN1 make a *click* sound again? connect a Gnd wire to IN1, does the relay on IN1 make a *click* sound?Ħ. connect the Gnd wires to a single pointĥ. NEVER USE RPI at this point.Īlso remember these "arduino relay modules" are active lowĢ. Using a separate 3.3V and 5V (not from RPi) do some test.
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