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Logic gate HIGH/LOW to enable/disable BLDC controller

ronsimpson

Well-Known Member
Most Helpful Member
I know I asked before but I can not find the answer.
SIGNAL 2.4V; What does it look like. Is it at 0V and 2.4V?
TORQUE 4.8V; Is that oV and 4.8V?
Do you want CONTROLLER to be the same as SIGNAL when signal is 0V? and CONTROLLER to be 0V when SIGNAL is 2.4V?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
It's not quite as simple as removing the caps, you need to conder the voltages at each stage and in each state.

Can you confirm what combination of input levels (torque and signal) should give which output level?
eg. the high and low voltage limits on each input; the output is presumably switching between 0V & 5V ?
 

BikerMark

New Member
Yep, confirm:
SIGNAL: 2.4V with 0,26 mA (remainder of luminated LEDS) or 0V (pulled to ground at brake lever)
TORQUE: 4.8V with 1.2 mA (remainder of 5V to the sensor which has appearantly a voltage drop of 0.2V) or 0V (sensor not cunductive)

When both are HIGH: CONTROLLER should get 5V.
If one of them is LOW: CONTROLLER should get 0V.

Hope this provides enough info to help me in the right direction!
 

rjenkinsgb

Well-Known Member
Most Helpful Member
OK, you need an AND gate, in principle.

Is the input to the controller naturally high or low, if nothing is connected? Or is it high impedance?
(To figure out if it needs an active pull up or pull down).
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Diodes were my original suggestion, but apparently did not work.
The 2.4V "high" may be holding the output too low for the controller.
 

Pommie

Well-Known Member
Most Helpful Member
Just reread the original post and it does say LOW is brake on - could have sworn it said the opposite. My apologies, A diode (or two) was all that was needed.

In an earlier post the OP said he measured 5V on the pin but could ground it without a problem from which I concluded (guessed), high impedance input with pullup.

Mike.
 

BikerMark

New Member
Is the input to the controller naturally high or low, if nothing is connected? Or is it high impedance?
(To figure out if it needs an active pull up or pull down).
I'm not quitte sure about this impedance thing. How to determine?
Input to controller must be naturally LOW, otherwise the motor would be activated by default, I deducted.

OK, you need an AND gate, in principle.
So, this is what I need to build?
120788
I do understand the working principle of this setup. But to complete it with values and types (T1,2 and R1,2) is yet another gray area to me.
Any suggestion and clarification is highly appreciated!
 

ronsimpson

Well-Known Member
Most Helpful Member
So, this is what I need to build?
The two transistor circuit is "ok" but the output will be 0 and 1.7 volts. I think that is too small.

Data sheet SN74LVC1G08. Is a AND gate. Logic levels on input. below 1.5V=0, Above 1.75=1 when using a 5V supply.
120790
Comes in this small package. Surface mount may be hard to use.
120791
The SOT-23 package is the largest. The SON package is hell to use.
120792
 

Pommie

Well-Known Member
Most Helpful Member
Besides, I noticed that EL was carrying +5V by default. I connected it to GND without any resistor (in line with the description of the controller), which did not cause any short circuit.
You said this in post 6 and this suggest that the input is high impedance. Can you measure the current to ground with your multimeter?
Indeed; when I measure voltage it is:
while active (LED is continiuously ON, this is the signal which is forked): 2.45V
while braking: (Led still ON, and enhanced by braking Light): 0.00V (maybe 0.01V, in fact LOW)
This suggest that the LED is being modulated to be both rear light and brake light. Do you have a Hz function on your multimeter? The 2.5V may be 5V at a 50% on time and 0V may be 100% on time.

Mike.
 

BikerMark

New Member
Current on EL to GND is 1.41 mA.

Tried to measure frequency on SIGNAL, but got strange behaviour on the multimeter: 0, (...5 seconds...) 0, 300, 0 (...5 seconds...) 0 659 .... didn't rea out the unities. I'm gonna do some homework and check again.
 

BikerMark

New Member
The SOT-23 package is the largest.
Have ordered them, going to layout a board on this chip, thnx!

EDIT: Very nice collateral pro: output is VCC, so the desired gain/amplifying (which brought me to my latest scheme) is not neccessary anymore. Looks like a briljant tip!
I wonder how to bring down 7V to 5.5V for VCC. Simply a resistor, or would a (series of) diode(s) do as well?
 
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