I am hoping to use my K8055 as an output device for in game force feedback - very similar to the kind of thing you will find on x-simulator.de
It is my intention to use the x-sim software package to control the K8055 card (this works already) and output power to two 12V windscreen wiper motors through either a mosfet H-bridge or other bi-directional dc motor speed controller. These motors will power the simulator platform.
Could anyone suggest a design for a suitable motor control setup, and also advise how best to connect it to the K8055 to make best use of PWM for speed control
I know I’m asking a lot, but if this is possible it opens up exciting home simulator builds for those of us with limited skills and knowledge - tronicgr has some superb designs, but making custom PCBs is so far beyond me it isn’t funny… pretty much my limit is trackboard
The following was posted previously as a solution for bi directional motor control using PWM…
That looks simple enough to put together… even for me!
I’m guessing that if I just use this circuit with current components and increase the power going through it to power my wiper motors, it will melt or explode or take out my K8055 - or all of these!!! (and even though I like spectacular experiments, I really really like my k8055! )
what values would I need for alternative components?
Many thanks in advance to anyone who takes pity on the noob! lol
You should check (measure) how much current the wiper motor is drawing and select other transistors if higher than 3A.
In any case you have to use a large heat sink for the transistors.
Please see this thread how to assemble the transistors to the heat sink avoiding short circuit: viewtopic.php?f=3&t=3899
See the pictures:
“Shoulder washers used on both the transistors, and on the heat sink”
and
“Mica insulators (non conductive thermal compound will be applied when it’s all done)”
I cant get hold of TIP31 or TIP42 from my local shop, but have increased the spec of the replacements I had in mind to:
2N3055: V:60, A:15, W:115 for the high power NPN and
TIP2955: V:-60, A:-15, W:90 for the high power PNP
As the car fuse was rated at 10 Amps, these should be sufficient!
One last question:
There are 3 outputs - I guess the I/OA and I/OB go onto two of the digital outputs, but what does VSS connect to - is that the ground or could it be used on the PWM output?
After a closer look, I noticed that the circuit diagram you posted is not usable with the K8055 as is. In this circuit the inputs I/O A and I/O B should be connected to active (high / low) outputs. The digital outputs of the K8055 are active low.
The alternative may be a relay solution:
More easy
No heat sink needed
No voltage loss
Please see this thread: viewtopic.php?f=15&t=3839&p=13222
There is a relay solution. - You may remove the transistor if you do not need speed control.
To get the motor running, activate (pull down) the K8055 outputs connected to In1 and In2. The K8055 outputs connected to In3 and In4 must be deactivated (open).
The motor current goes through Q1 and Q4.
To reverse the motor voltage you should first deactivate the outputs connected to In1 and In2. Then activate (pull down) the outputs connected to In3 and In4.
The motor current goes through Q3 and Q2.
It may be good idea to add a 10A fuse in series with the battery to protect the circuit.
OK… using this design I made my first custom PCB, managed to assemble the circuit without lifting any tracks, and only got one of the pairs of transistor legs the wrong way… but incredibly… eventually…
[size=150]IT WORKS!!![/size]
Once I got over the problems (basically my inexperience and lack of soldering skill) The circuit did exactly what it should, but with huge power loss - I think i’m losing most of the energy heating the red hot components!
Having now tested this though, I have some more questions:
Why is it necessary to feed outputs 1 and 2 or outputs 3 and 4 rather than just having 2 outputs - say on 1 and 2?
Is there a way that speed control could be built in to this circuit using the PWM outputs?
It’s good to see that you got the circuit working!
[quote]The circuit did exactly what it should, but with huge power loss - I think i’m losing most of the energy heating the red hot components![/quote] Indeed, if you look the datasheet there is written:
Collector-Emitter Saturation Voltage
IC = 5A, IB = 10mA 2V
IC = 10A, IB = 40mA 3V
This means that at 5A the power loss in the transistor is 2V * 5A = 10W.
If the current is 10A then the power loss is 3V * 10A = 30W per transistor.
You just need huge heat sink…
[quote]1. Why is it necessary to feed outputs 1 and 2 or outputs 3 and 4 rather than just having 2 outputs - say on 1 and 2?[/quote] If you like to use only two outputs of the K8055, then the circuit will be more complicated. To eliminate all extra transistors, the four open collector outputs of the K8055 are used to control the operation.
[quote]2. Is there a way that speed control could be built in to this circuit using the PWM outputs?[/quote]This may be easily done. Just connect the base of the transistor Q2 also to the PWM1 output and base of Q4 also to the PWM2 output of the card.
Keep the connection to all the four digital outputs as is.
The PWM output pulls the base of Q2 or Q4 down reducing the motor speed. High PWM setting means long low time and low speed.
Begin with PWM setting 0. Then slightly increase to see the effect.
I’m not happy any more - my questions have been hijacked!
I want a solution IN TERMS of the original diagram. I can go to any one of dozens of electronic enthusiasts for a solution that doesn’t involve the MOSFET. Please stick to topic if you really want to help me. Otherwise I’ll drop off here and look for answers elsewhere taking with me the best solutions so far …
[quote=“John Broadley”]I’m not happy any more - my questions have been hijacked!
I want a solution IN TERMS of the original diagram. I can go to any one of dozens of electronic enthusiasts for a solution that doesn’t involve the MOSFET. Please stick to topic if you really want to help me. Otherwise I’ll drop off here and look for answers elsewhere taking with me the best solutions so far …[/quote]
I apologise sincerely for being such an insensitive and offensive bore–I will try to better myself…
Thank you for the clarification–I was going to draw something up when I had time, until that last outburst–best now that he take his ball and go home.
It sounds to me as though he has a school project for which he would like someone else to engineer the solution; otherwise why would the exclusive use of a MOSFET such a big deal?
)
