MicroPython Forum (Archive)

@pythoncoder Cool, that you still have it. That one looks very good. I made a similar one, just not so nice, based on a Z80. All parts handwired and soldered. Starting with a hex display for address and data, a single step mode & button, and an old teletype from trash for input/ouput. Then slowly expanded, whenever I had money for it, up to a CP/M system with two diskette drives. Even those, starting single density, single side, then step-wise up to double density, double side. I used that computer even in the first years of my first job as engineer. A few months ago, I found a few boards of that device, and threw them away. How much time must I have had to make them!

I made indeed my first sparkling experience with tube radios from trash, trying to get them working or to make other use of them. The older ones not even had a transfromer for separation form mains. Not to mention TV sets. I always denied that I can repair TV's. Too painful.

@johnv: Sorry for hijacking the thread. Just three old men talking about the war.

Roberthh wrote: ↑

Sun Dec 08, 2019 9:14 am

@pythoncoder Cool, that you still have it...

Alas I have only the photos. The peripherals had long gone so - eventually - it went too

...@johnv: Sorry for hijacking the thread...

Indeed.

so i could put from an external source 5v dc to the realy 'vcc'-pin and on the 'in'-pin the nodemcu output (pin 4),

but i tried that and the signal on the output pin, was to weak i guess, it just switched once and never again.

any ideas how to work around this one?

haha great stuf;

i am quite greatefull with chinatec these days

at least we can have half reliable stuff for cheap, i cant imagine what it would have cost for a simple project to get up and going, if you have to bin somtransistor as from the above you got a realy bad week for smokes

btw can you replace a 2n7000 with a 2n2000? or did i read that wrongfully on the internet?

and it would be to power the 3v relay wright?

btw if there is a solution for driving the 5v relay i would be greatly be interristed, tnx guys!!!

btw, dont care about the hijack, love to hear from the old stuf, now days everything is so small, its (nearly)imposible to solder something out without wasting the component, its all dubble layerd pcb, if somthings faulty, its to the bin and buy a new part

No. It is a 2N7000.
You have to connect GND between NodeMCU and the Relay board, +5V (and GND) to the relay board, and then try to switch with a GPIO. I If you have a multimeter, you could measure the voltage at the Relay board input, when that board is powered, but the input is not connected. You could also just connect it's input to GND or Vcc and tell, when the relay is switching. If it switches when connected to GND, then you will need that additional transistor/gate between NodeMCU and Relay. if it switches when connected to Vcc, the GPIO output of the NodeMCU should be sufficient.

just measured the input when not connected and it is 4.28v

Roberthh wrote: ↑

Sun Dec 08, 2019 11:08 am

No. It is a 2N7000.
You have to connect GND between NodeMCU and the Relay board, +5V (and GND) to the relay board, and then try to switch with a GPIO. I If you have a multimeter, you could measure the voltage at the Relay board input, when that board is powered, but the input is not connected. You could also just connect it's input to GND or Vcc and tell, when the relay is switching. If it switches when connected to GND, then you will need that additional transistor/gate between NodeMCU and Relay. if it switches when connected to Vcc, the GPIO output of the NodeMCU should be sufficient.

yes it clicked when the IN was connected with ground!

but i dont have that 2n7000 transistor right now,

i bought this 2 transistor boxes a while a go, if i had to tinker with something, i tought these would have the most important in it, can you see if there is something usefull in it please?

https://nl.aliexpress.com/item/32856312 ... b201603_55

and this one:

https://nl.aliexpress.com/item/32867646 ... b201603_55

i just bought a 100pcs pack of 2n7000 of amazon for 16euro, should rlast me some projects

You can use the BC337 or 2N2222. But these are NPN transistors. So you need a resistor between base and GPIO output. Size 2.2kOhm -> 10 kOhm. The MOSFET like 2N7000 do not need a current limiting transistor at the gate.
Using the NpN-Transistor:
Emitter to GND
Base via resistor to GPIO out
Collector to Relay Board input

Using the 2N7000:
Source to GND
Gate to GPIO
Drain to Relay board input

P.S.: The second box in your link are voltage regulators, not transistors.

tnx man, got a little smarter today