Need advise: Conversion from relay contacts to transistor for motor forward reverse.

Thread Starter

Benx

Joined Jun 2, 2017
9
Hi, I need advise to convert these relays contacts to transistors. I cannot find anywhere this designs in internet. So I come here to ask hekps from masters of electronics.
Is there any IC to replace this method insteads of using too many transistors. If able to use IC, this will reduce complications and pcb space.
What will be the differences if L is 5V vs 12V?
If one relay is switched on, the other relay must not switch on.
Is there possible to a third relay? The rule also applies, 1 relay switch on, the other 2 must not switch on.

rever forwad daigram.jpg

* MC-1 NO and MC-1NC contacts are belong to MC-1 Relay.
* MC-2 NO and MC-2NC contacts are belong to MC-2 Relay.
* Use transistors or IC to replace all of these contacts of MC-1 NO, MC-1 NC, MC-2 NO and MC-2 NC.
* Voltage on L is 5V or 12V.
* Please ignore the contacts for motor side. I took this picture from the web. It is similar but not for motor forward reverse.
 
Last edited:

drc_567

Joined Dec 29, 2008
887
Here is a generic circuit, an H-Bridge, for motor direction control:


...Could you describe your requirements again? Would turning on/off a pair of the Mosfets, shown in the circuit, accomplish your purpose?
 

Thread Starter

Benx

Joined Jun 2, 2017
9
Here is a generic circuit, an H-Bridge, for motor direction control:


...Could you describe your requirements again? Would turning on/off a pair of the Mosfets, shown in the circuit, accomplish your purpose?
Thanks for your time. Actually, I need to activate 3 relays and when 1 of the relay is switched on, the others must not switch on. If someone can teach me on 2 relays, then I will crack my head to make it to 3 relays design. I do not want to stress you guys.
I had seen the H-bridge but it is not the same design.
I took this picture from the web. It is similar but not for motor forward reverse. Its another requirement for another function. A motor with 3 coils speed. If more than 1 coil is switched on, it will damage the whole coil. So only 1 relay can switch on at a time.
 

dendad

Joined Feb 20, 2016
3,602
I don't understand why you need 3 relays.
Also, it does not matter if both relays operate at the same time as they are cross connected and all it will do is to short out the motor with the connection to +V, just the same way as both relays being off, motor shorted out with the connection to ground.

If you cannot build it yourself, there are a lot of DC H-Bridge boards on Ebay..
http://www.ebay.com.au/itm/Semiconductor-Motor-Driver-Auto-BTS7960-43A-H-Bridge-PWM-Drive-For-Arduino-L3-/272393034753?hash=item3f6be3dc01:g:H4sAAOSwTA9X6zpK

http://www.ebay.com.au/itm/Dual-H-Bridge-Stepper-Motor-Drive-Controller-Board-Module-For-Arduino-L298N-GK-/371541113308?hash=item56819379dc:g:nYUAAOSwL7VWpx97

http://www.ebay.com.au/itm/Dual-Motor-Driver-Module-Board-H-bridge-DC-MOSFET-IRF3205-3-36V-10A-30A-TE589/262749416039?_trksid=p2045573.c100505.m3226&_trkparms=aid=555014&algo=PL.DEFAULT&ao=1&asc=20151005190540&meid=af35e188e99d43c1a6037d28e0519e15&pid=100505&rk=1&rkt=1&

Pick the size depending on your load.
 
Last edited:

dendad

Joined Feb 20, 2016
3,602
Just an afterthought, The LM298 boards will run with switch inputs, but some other boards will need a PWM signal, not a DC in, so they can develop the gate drive for the top FETs. The boards with the FETs may be like that. I've not used them, but one addvert says 0 to 99%PWM so that is a hint they cannot run with just switched DC on both inputs.
You could have a 555 running as a PWM speed control and switch just the direction so that overcomes that problem.

https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf

http://www.bristolwatch.com/ele/h_bridge.htm
 
Last edited:

drc_567

Joined Dec 29, 2008
887
Another guess ... how about a single push button that cycles through each relay/switch, as the button is pushed? Only one relay activated at any particular time ...
...Or do you need to select a single specific relay at each button push?
 

Thread Starter

Benx

Joined Jun 2, 2017
9
Another guess ... how about a single push button that cycles through each relay, as the button is pushed? Only one relay activated at any particular time ...
...Or do you need to select a single specific relay at each button push?
Yes, single each. This is the design.

Just an afterthought, The LM298 boards will run with switch inputs, but some other boards will need a PWM signal, not a DC in, so they can develop the gate drive for the top FETs. The boards with the FETs may be like that. I've not used them, but one addvert says 0 to 99%PWM so that is a hint they cannot run with just switched DC on both inputs.
You could have a 555 running as a PWM speed control and switch just the direction so that overcomes that problem.
I had also referred to some flip flop IC but they have too much uncertainty. The simpler digital IC still cannot do this job. L298 cannot turn on just switch dc. Its also a different design.
 

dendad

Joined Feb 20, 2016
3,602
L298 cannot turn on just switch dc. Its also a different design.
Yes it can. Just pull the inputs high with a resistor, and have push buttons to pull each input to ground, depending on your direction.
With both inputs HIGH or LOW, the motor is in Brake condition.
And to increase the current, you can parallel both halves of the chip.
 

Thread Starter

Benx

Joined Jun 2, 2017
9
Yes it can. Just pull the inputs high with a resistor, and have pushbuttons to pull each input to ground, depending on your direction.
With both inputs HIGH, the motor is in Brake condition, and if you push both buttons together, the motor is in freewheel.
And to increase the current, you can parallel both halves of the chip.
Actually the motor is AC and the relays are driving it with only 1 rotation but different speed according to that relay. There are 3 speed coils inside this motor sharing same neutral.
 

dendad

Joined Feb 20, 2016
3,602
Actually the motor is AC and the relays are driving it with only 1 rotation but different speed according to that relay. There are 3 speed coils inside this motor sharing same neutral.
Ah! That is a different application that was not apparent from your original post, at least to me.
You could use opto isolated triacs (or Solid State Relays), and to prevent more than 1 turning on at once, feed your switches into the input of a decoder like an old school 74AC138, and select the output to drive the triac.SSR.
That way only one triac can be on at a time. Can you figure that out or do you need a circuit?
EDIT: Here is a quick scribble...
138MotorControl.jpg
 
Last edited:

Thread Starter

Benx

Joined Jun 2, 2017
9
Ah! That is a different application that was not apparent from your original post, at least to me.
You could use opto isolated triacs (or Solid State Relays), and to prevent more than 1 turning on at once, feed your switches into the input of a decoder like an old school 74AC138, and select the output to drive the triac.SSR.
That way only one triac can be on at a time. Can you figure that out or do you need a circuit?
EDIT: Here is a quick scribble...
View attachment 128080
Thank you! This is a nice solution. But is there any 12V type instead of only 5V or any other equivalent IC? The DIP pin type for this IC is so rare in ebay. Is it obsoleted or replaced by another type?
 

dendad

Joined Feb 20, 2016
3,602
You could look at the CD4028, but check for different pin outs.
Also, the outputs are active high, not low like the 138.
 

Thread Starter

Benx

Joined Jun 2, 2017
9
You could look at the CD4028, but check for different pin outs.
Also, the outputs are active high, not low like the 138.
I think this is the better solution. Now I have to crack my head on thinking how to connect output cd4028 --> optotriac --> transistor --> relay and switch --> transistor --> input cd4028.
Sorry my electronics is considered very poor because my work neglects electronics.
How do you remember and know all those IC?

It simple. What current you need?
no suggestion?
 

EM Fields

Joined Jun 8, 2016
583
Hi, I need advise to convert these relays contacts to transistors. I cannot find anywhere this designs in internet. So I come here to ask hekps from masters of electronics.
Is there any IC to replace this method insteads of using too many transistors. If able to use IC, this will reduce complications and pcb space.
What will be the differences if L is 5V vs 12V?
If one relay is switched on, the other relay must not switch on.
Is there possible to a third relay? The rule also applies, 1 relay switch on, the other 2 must not switch on.

View attachment 128033
* MC-1 NO and MC-1NC contacts are belong to MC-1 Relay.
* MC-2 NO and MC-2NC contacts are belong to MC-2 Relay.
* Use transistors or IC to replace all of these contacts of MC-1 NO, MC-1 NC, MC-2 NO and MC-2 NC.
* Voltage on L is 5V or 12V.
* Please ignore the contacts for motor side. I took this picture from the web. It is similar but not for motor forward reverse.
Rather than posting schematics which are "similar" to what you want and will likely yield answers which are "similar" to what you need, why don't you just explain what it is you're trying to do, post data sheets for the components you want to use, and let us take care of the rest of it?

After all, if you're in a strange city and you hire a taxi to take you to certain location, it would be fairly rude to tell the driver the way you think he should go.
 

Thread Starter

Benx

Joined Jun 2, 2017
9
You could look at the CD4028, but check for different pin outs.
Also, the outputs are active high, not low like the 138.
I am too busy with another diy now. But I must say this in case I had forgotten: "Dendad, Thank you for your time and help. I really appreciated."


Rather than posting schematics which are "similar" to what you want and will likely yield answers which are "similar" to what you need, why don't you just explain what it is you're trying to do, post data sheets for the components you want to use, and let us take care of the rest of it?

After all, if you're in a strange city and you hire a taxi to take you to certain location, it would be fairly rude to tell the driver the way you think he should go.
I wish I have the time and way.I am too busy with my kids too because my wife health is not in good shape.
 

EM Fields

Joined Jun 8, 2016
583
I am too busy with another diy now. But I must say this in case I had forgotten: "Dendad, Thank you for your time and help. I really appreciated."



I wish I have the time and way.I am too busy with my kids too because my wife health is not in good shape.
My sincere condolences.
 
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