• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Logic gate HIGH/LOW to enable/disable BLDC controller

rjenkinsgb

Well-Known Member
Most Helpful Member
Ron -
I'd also allow for a base-emitter resistor as the levels are not exactly known. That will allow some adjustment if the off state voltage is not low enough or has some noise on it.
 

BikerMark

New Member
Yo guys, update time!
The setup in the scheme didn't work out. I have tried several variations, they all did not pull down the EL without affecting the braking light.

Sitting next to my bike with my breadboard and the stuff I bought yesterday, I came up the idea to not use the EL, but interrupting directly the throttle line.

Now, Signal (dis)allows 5V to the optocoupler, which interrupts the throttle if Signal drops.
120684
1N4007 as a safety measure; I noticed some (what I call) leakage current towards the base in 2N2222A.
I'll be routing this schema to this compact board (22x17mm):
120687

Thank you all, again, for your help. I hope I may call once more in the future!
Mark
 

ronsimpson

Well-Known Member
Most Helpful Member
No. Will not work.
120688
Because the drive voltage is only 2.5 volts (voltage on pin 2 of H2) you will never get current to flow in the 4N35.
Put the emitter of 2N222a on ground. Connect the 1.3k and 4N35 on the collector and supply.

What does the voltage and current on "EL" look like? I am not certain that the 4N35 will work.
 

ronsimpson

Well-Known Member
Most Helpful Member
I added voltages to the schematic. You need to lift H2 pin 2 to 5.8 volts to get good current to flow in the 4N35.
120693
 

BikerMark

New Member
Wow! That's amazing; how do you calculate/predict these voltages? Has it to do with known voltage drops acrros the components?

It was my concern too, to have too few volts on 4N35, but on my breadboard it worked. I measured on pin 1 a louzy 1.8V (or nearby) but to my relieve it drove the connection on 4 and 5.

Board is just about to be finished; I hope this week to solder the comps and see whether it works.
I'll keep you updated.

What does the voltage and current on "EL" look like? I am not certain that the 4N35 will work.
The voltage on EL is 5.1V, I do not know how to measure its current. Simply connect a multimeter-probe whith the switch on mA (start at full Amps, probably). EL is set HIGH by the controller, of which I do not have a diagram, only some data:
BLDC controller
 

ronsimpson

Well-Known Member
Most Helpful Member
If the controller can lift to 5.1V then the diode drops that by 0.65. (about) (could be removed)
The transistor B-E will also drop the voltage by 0.65.
The 4N35 LED will drop 1V at 2mA
5V-0.65-0.65-1V= 2.7V on 1.3K resistor. So 2mA (about)
2mA is small!
This only works because the controller can lift to 5V.
 

BikerMark

New Member
Apparently I do not undertand the 2N222a. I thought it is meant to switch any higher voltage by a smaller one.

That explains my choice to feed its base with the 2.8V, provide 5V on collector and expect even more than 5V on the emitter.

Why this is not happening in my set-up (on breadboard)?
 

ronsimpson

Well-Known Member
Most Helpful Member
"Emitter followerer": The output voltage will be about 0.65 volts below the input. With your input of 5.1V the output will be 4.45 volts.
I teach students. Their books say "apply current (voltage) to the base (gate) of a transistor and it will turn on. They think if you put 1V on the "in" the output voltage will to 12V. Every year (semester) we have the same problem. I want to through away the book.
120695
The 2N2222 must have B-E current for it to turn on. The B-E looks like a diode. With the base at 5V the transistor will turn on until it pulls the emitter to 4.4 volts. The transistor can not pull up more because the B-E voltage will drop below 0.6V and turns off the Collector.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Apparently I do not undertand the 2N222a. I thought it is meant to switch any higher voltage by a smaller one.
Sorry to be somewhat 'rude', but it's obvious that you don't understand the slightest thing about electronics or electrics, not a single thing you've posted makes the slightest sense - you just seem to randomly connect transistors together, ignoring all the requirements for resistors etc. to make an actual circuit.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
There are three different configurations for a single transistor used as an amplifier or switch, all with different functional properties:

Common Emitter - emitter to ground, input to base, output from collector.
That inverts the signal and can give both voltage and current gain.

Common collector (aka emitter follower) - collector to power, input to base, output from emitter.
That provides current gain only, the output voltage follows the base, less one diode drop, eg. 0.6 - 0.7V for a silicon device.

Common base, the rarest one. Input to the emitter, base connected to a bias or reference voltage, output from the collector.
That provides non-inverting voltage gain but no current gain.
 

Pommie

Well-Known Member
Most Helpful Member
As the input appears to be high impedance with a pullup, a 2N2222 with collector to EL, emitter to ground and base to brake signal via a 1k resistor should be all that's needed. Why the complication of optos and relays?

Mike.
 

BikerMark

New Member
Sorry to be somewhat 'rude', but it's obvious that you don't understand the slightest thing about electronics or electrics, not a single thing you've posted makes the slightest sense - you just seem to randomly connect transistors together, ignoring all the requirements for resistors etc. to make an actual circuit.
Correct. I was glad I could post a question here, and I'm learning from it. I've been given some good explanations (of which
There are three different configurations for a single transistor used as an amplifier or switch, all with different functional properties:
is the best for me so far on transistors.

I hope I'm allowed to learn further here and not spoiling anyone's time.

EDIT: Sorry to be somewhat rude too:
When it comes to doing things randomly and devellop one self:
I have a hard time to not destroy completely your 'site', which has been updated in 2006 (!). It's not fair to patronise me for having fewer knowledge on electronics than you have.
120701 lpilsley.co.uk
It's a huge ingnorance of contemporary webdesign.
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
I have a hard time to not destroy completely your 'site', which has been updated in 2006 (!)
The site has actually been updated quite regularly, with the last major update being earlier this year.
I suspect the IE graphic is just an ancient leftover..

And don't worry about asking questions, that's the way to learn!
 

BikerMark

New Member
The site has actually been updated quite regularly, with the last major update being earlier this year.
I suspect the IE graphic is just an ancient leftover..

And don't worry about asking questions, that's the way to learn!
Thanks for easying my grief on the questioning part. The site I was talking about is from mr. Goodwin: click here.
 

BikerMark

New Member
First of all, I want to say I'm sorry for my impulsive edit earlier. I should have left the reply as it was initially.

I hope the next scheme will show off some progress in my understanding of transistors:
120771
It is supposed to be a voltage gaining logical gate, fed by 7V. It's based upon two tutorials on amplifying: this one and this one. In my understanding the Voltage dividers (R1-R2 and R6-R7) are enhancing the input signal, while the ratio between R3-R4 and R8-R9 is important for the gain.

The scheme should block any output when either TORQUE or SIGNAL drops to (near) 0V. Though I'm affraid if Q1 does not conduct, current will flow through C2 and evantually reacht the CONTROLLER. If so, how to avoid this?

While both inputs provide current, CONTROLLER should receive a nice amount of Voltage (current is not needed too much). It can handle up to 5V (I'm curious what's going to happen when more is provided).
The precise values of resistors and capacitors is yet to be calculated. I now just copied the values of first tutorial.

Anybody any thoughts on this scheme? I'ld be pleased to hear them, and I sincerely hope this scheme starts making any sense...
Regards,
Mark
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Anybody any thoughts on this scheme?
You need to consider that capacitors block DC, so any changes or signals would be momentary & then return to the DC bias levels.

I'm guessing the examples you were looking at were for audio rather than logic systems; the two function rather differently.
 

BikerMark

New Member
Oops! Thanks for pointing that out.
Your assumption is right, I was unaware of those not being suitable for logic systems.

Can I simply cut out the caps? Or should I start from scratch all over again?
 

Latest threads

EE World Online Articles

Loading

 
Top