Replacing a jumper with an electronic control?

[pavjayt]

Hello All,

I have a circuit where I use jumpers to short traces (either trace 1 to trace 3 or trace 2 to trace 3). There is no power or ground involved here. To be specific I am connecting outputs from a 74HC4040 (Q8 or Q9) to reset pin of 74HC14 (MR). At present I have two jumpers each connected to Q8 and Q9 and the other ends of the jumpers to MR of 74HC14. At any given time I keep only one shorted using a jumper. Now I would like to replace that manual jumper setting with an electronic switch which I can control form a PC from my application.

Iniitally my idea was to use a small relay (SPDT), but then thought of using transistors too, but not exactly clear on how to use in my scenario.

Any ideas or suggestions are greatly appreciated.

thanks

 

[shortbus=]

A cd4066 may do the job for you - https://www.electro-tech-online.com/custompdfs/2012/07/CD4066BC.pdf

 

[pavjayt]

A cd4066 may do the job for you - https://www.electro-tech-online.com/custompdfs/2012/07/CD4066BC.pdf

Thanks, this looks exactly what I am looking for. One more question though, since the datasheet doesnt have any test circuits for a sample application, could you tell me how I can go by connecting it. I mean where I should use capacitor and or resistor on in and out of switches etc.

 

[shortbus=]

A search on this site will get a lot of hits and ideas. Search "cd4066"

 

[pavjayt]

A search on this site will get a lot of hits and ideas. Search "cd4066"

Thanks for the suggestion. I looked it up and sure there are many threads on this topic. At the end I decided on two switches with low RON, but not sure which one to use due to VCC ratings.

NX3L1T53 with 500mΩ RON while with a max VCC of 4.6V (who would design with such an odd voltage ?!?!)

DG9431 with 30Ω with max VCC of 12V.

My design has 5V supply and I like to use low RON. As I already mentionied I will be using this in between two 74VHC4040M ICs between either Q8 or Q9 of IC1 to MR of IC2 using the switch.

Any suggestions.

thanks

 

[ChrisP58]

Since you are going between logic inputs and outputs, the most obvious choice to me would be to use another logic chip.

Look at the 74HC157 and 74HC158.

If you want to stay with the analog switch idea, the 74HC4053, would work.

As far as wanting to use low RON switches, there is probably no need to worry. Unless you have something else loading the output of the switch, the microamps of bias current of the logic inputs can tolerate many thousands of ohms. Higher resistance will slow the signal down, but the difference will be well below a microsecond.

 

[pavjayt]

Since you are going between logic inputs and outputs, the most obvious choice to me would be to use another logic chip.

Look at the 74HC157 and 74HC158.

If you want to stay with the analog switch idea, the 74HC4053, would work.

As far as wanting to use low RON switches, there is probably no need to worry. Unless you have something else loading the output of the switch, the microamps of bias current of the logic inputs can tolerate many thousands of ohms. Higher resistance will slow the signal down, but the difference will be well below a microsecond.

Thanks for your input. I am planning to use one of the data pins of a parallel port to control the switch. So, in this case, can I substitute your logic switches rather than an analog switch?

Also, is there any problem if I use DG9431 switch, I only need one SPDT switch.

 

[ChrisP58]

The DG9431 should work. You might also look at the SN74LVC2G157. It is a single channel version of the 74HC157.