Hello, I have an 8 channel light transformer box with a 9 pin serial controller cable, and I’d like to get a K8055 to connect and control from a computer instead of the controller it came with. Pin 1 of the cable appears to be hot, and the other 8 pins correspond to the 8 channels. Testing with a multimeter revealed 12 volts, 200mA when the - was connected to pin 1, and + connected to any other channel.
From reading the K8055 manual, and looking around on this forum, it seems that aside from needing 200mA and the k8055 only supporting 100mA, I could connect pin 1 to the digital output block ground, and the other 8 pins to the 8 outputs? If that is correct, would it somehow be possible to use some different resistors (or do something else) in order to pass through the 200mA? I don’t believe the transformer actually needs the 200mA back in order to actually do the switching, since the controller it came with was powered by that one 9 pin cable too (and it has LEDs and a microphone and such).
If I won’t be able to use the K8055 for this, can anyone suggest a similarly priced unit?
I’m sorry, but you can’t change the maximum switching current of the K8055. This is 100mA /channel. This current is limited by the transistor array IC ULNxxx.
These outputs are “open-collector” output, so there is no voltage coming out.!
I’m guessing then somehow I could use a transistor attached to the outputs that could then perform the switching? I did actually buy the K8055 2 days ago and am waiting for it to ship- I’m guessing there is some way to do what I’d like to with it, but I’m really only familiar with more basic electronics (I figure assembling the kit won’t be a problem, since I’m good with instructions).
The specified 100mA digital output sink current for the K8055 is on safe area. No need to worry about the transistor array total power dissipation in normal room temperature. According to the datasheet the maximum current of the transistors of the ULN2803 array is 500mA.
If you anyhow exceed the 100mA limit, on your own risk, you have to take care not to exceed the ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS. See the graph in the datasheet: ortodoxism.ro/datasheets/all … /2801.pdf’
See also the graph “ALLOWABLE COLLECTOR CURRENT AS A FUNCTION OF DUTY CYCLE” on page 6. There you can see the maximum allowable current vs. the number of outputs conducting simultaneously. If all the 8 outputs are conducting simultaneously then the max. current is about 170mA @ 50°C and about 150mA @ 70°C. The specified 100mA limit for the K8055 is still on the safe area.