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    Would anybody help with a basic circuit design and spec please

    @JillKent, there are free online schematic drawing tools to make for user easy schematic creation, which will get you clear readable schematics for posting. Just google for them. Or use the free available spice simulators or free PCB design tools for schematic creation. Regards, Dana.
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    Hello, I want to reduce 12 volts to 7 volts, how many ohms do I need using a resistor?

    Post #2 has a number of pertinent questions.....
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    Hello, I want to reduce 12 volts to 7 volts, how many ohms do I need using a resistor?

    How much current do you need ? Does the load vary in current draw ? What is accuracy of 7V you need ? What is range of 12V input ? What is 7V load ? A motor, bulb, radio.....? These are all specifications you need to do a proper design.
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    Need simple overvoltage protection - can I use a 7805?

    Protecting 3 Terminal regulators : https://www.ti.com/lit/pdf/snva517 https://www.renesas.com/document/man/usage-three-terminal-regulators The above discusses protecting the regulator, eg. function of various diodes. Note you are trying to protect the module I gather. So "normally"...
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    Would anybody help with a basic circuit design and spec please

    Yes and No. Yes you could trim the input to sit at the threshold of turning relay on but power supply variation due to T and V would easily raise havoc tripping relay when not desired. Its called noise margin when controlling something on/off. The wider the Vin-Vil the better in below graph...
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    Would anybody help with a basic circuit design and spec please

    Sounds like just the series R into the OptoLED will do the job. I would calc it for 5 mA, should give you plenty of margin. Regards, Dana.
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    Would anybody help with a basic circuit design and spec please

    The 2.3 mA the coil or OpTo LED current ? Looks like no mark for CTR : So try post #26, hopefully your CTR is good (high). Regards, Dana.
  8. D

    Would anybody help with a basic circuit design and spec please

    If one looks at the PCB for the module one can see there is an optocoupler as input then feeding a NPN transistor to drive relay. So if relay is roughly 50 mA coil, then transistor base from optocoupler must supply ~ 5 mA to insure transistor is saturated. So looking at Opto its marking for CTR...
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    Would anybody help with a basic circuit design and spec please

    The 14V will, in general, give you extra margin, so should be OK. Optocoupler considerations : https://www.we-online.com/components/media/o760909v410%20ANO007a_EN.pdf https://www.vishay.com/docs/83741/83741.pdf Regards, Dana.
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    I want to ask a few questions. Can I control a 380 DC motor using Arduino with a driver card? And I want to ask another question. Can I calculate the

    If the driver card is rated for the power and current and voltage of the motor, with margins. What are the motor ratings ? What card are you contemplating ? To measure RPM you would use an optocoupler to allow Arduino to count, over a time interval, shaft rotations ...
  11. D

    Would anybody help with a basic circuit design and spec please

    I had an error in Opto LED current needed. Eg. R2 value. Here is approximate solution, based on what I think is Opto Coupler on your module. One should do worst case, eg. lowest value of 12V supply, lowest value of CTR in opto coupler, eg, margins, but try this out. Note R4 is relay internal...
  12. D

    Would anybody help with a basic circuit design and spec please

    If you use module then this is interface to input to optocoupler. It would be helpful to know what the part number is of the optocoupler. To make sure you give it enough drive thru LED to turn its output transistor hard on. OK, I think I found opto coupler datasheet and 5 mA is roughly what...
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    Would anybody help with a basic circuit design and spec please

    All my earlier comments on what to use are not for using a module, just individual components. Otherwise the interface has to account for the low V from LED/Laser signal, eg. make that signal bigger.
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    Would anybody help with a basic circuit design and spec please

    We start with relay, pick a 12V relay that meets your contact V and I. Then we need to know its coil current to energize it. So R1 = (Vlaser - Vbe*) / ( Icoil / 10) so assuming I coil is 100 mA then R1 = (1.8V- .7V) / (.1A / 10) = ~ 1.1 / .01 =~ 110 ohms. But use the Icoil from the relay you...
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    Would anybody help with a basic circuit design and spec please

    "Normally" one drives a relay like this : R1 limits base current. To saturate (hard turn on, lowest Vce) transistor Ib =~ Ic /10. Ib = Ibase, Ic = Icollector of transistor. Vce is V collector to emitter of transistor. Ic would be relay on current needed. R2 is for cases where the base can...
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    Would anybody help with a basic circuit design and spec please

    I cant find on any sites what the high level logic level input spec is on the module, other than an inferred 3.3V. Maybe set up on bench with variable supply and raise V until you see contacts close with a ohmmeter. I also saw some comments that they had to use 5V to get relay coil to activate...
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    Would anybody help with a basic circuit design and spec please

    Datasheet or specs for the relay coil ? Do you want a triggerable relay, one pulse turns it on and it stays on until another pulse to turn it off and stay off, rinse and repeat ? Regards, Dana.
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    amplify load cell output

    The low cost 620 not great in common mode range, in and out. Just keep that in mind when designing. Regards, Dana.
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    amplify load cell output

    https://www.digikey.com/en/products/filter/instrumentation-op-amps-buffer-amps/687?s=N4IgTCBcDaIIYBMBsYAsIC6BfIA Its not the only part that one can consider : https://www.analog.com/en/product-category/instrumentation-amplifiers.html...
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    amplify load cell output

    Sounds like you want a load cell to control a VCO.....? For amping up the load cell an easy way https://www.analog.com/media/en/technical-documentation/data-sheets/AD624.pdf Many VCO type 555 circuits on web, here is one : https://www.electroschematics.com/wide-frequency-range-555-vco/...
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