Not finished the cable yet... but I did forget the heatshrink... will definitely insulate the connections... I have lots more to make so I will be sure not to forget the heatshrink... Thanks

@Richard, What is that transistor your using in your picture? Have you tested it yet to see if you get a stable 5vdc from 3.3?

Hey Dave... it is a standard LM7805.... it gives a steady 5v... I think they are rated at 1.5amp as well... Overkill for basic sensors, but I had a bunch so I spliced a handful into some servo wire extenders...

Figured I'd mention that the ultrasonics that come with our Dev. Kits have an inline 5V regulator attached to them, I'm pretty sure we'll be offering them separately on the website but I'm not certain. I'll look into it.

As for sharp infrared sensors, little known fact is that they can operate at 3.3V. The distances may not be to exact specifications but we have tested them and they still exhibit a linear response. Just hook them up to the analog ports like on the v3.

Thanks to both of you.

Here's what I need to do, I need to bump up the signal voltage on a V4 of pin D0 to 5v like the old the old V3 provided. I built a high side switching out of a couple mosfets (Driver and pre-driver) that I was using with the V3. However the 3.3 vdc that now comes from the v4's D0 signal pin wont open and close the transistor. I thought It would be eaiser to bump up the voltage with a converter rather then rebuild the switching board. Not sure it will work though. The V4 not providing 5v anymore is sure a pain when retrofitting. However it's one of the only pains I've felt so far.

Hi @Dave,

I thought the same thing when we started the V4 design, but to my surprise almost all the accessories that we used with the V4 that specified 5V logic could actually be used with 3.3V logic. This is because a 5V logically high is considered a "high" down to 2.7V and since 3.3v falls in that range it all works out. Another nice this about the v4 are the 5V tolerant pins. This means the v4 can handle 5v signals coming back to it.

Something to consider when using a transistor is that they are current controlled, voltage doesn't play too much of a factor. When moving from 5v to 3.3v logic all you will have to do is lower the resistor value going to the base of the transistor and things should return to normal functionality.

Thanks Skater, I was thinking the same thing. I also thought lowering the resistor value may work. Thanks for confirming this. Here's my circuit I designed and built. I think I'll start lowering R2. What do you think? Maybe by 1/2 the value?

Jeremy beat me to it there but since I want to chime in and have a few minutes, and for the benefit of everyone who isn't clued up on ohms law...

Ohms law states that V = I x R, in other words, Voltage is equal to the current multiplied by the resistance. To work out the new resistance required due to the drop in voltage from 5v to 3.3v we just need to apply Ohms law.

As we will need to find out I and R too, we can use the Ohms Law Triangle;

This basically tells us that; V = I x R I = V / R R = V / I

We want to find the new R to push the current back up to what it was. So first we need to find out what the current (I) was...

Assuming the original resistor is 10k ohm;

I = V/R

I = 5/10000 I = 0.0005A or 0.5mA

Now we have dropped the voltage to 3.3v the current will have changed, this calculation isn't necessary but just for completeness I'll show it;

I = 3.3/10000 I = 0.00033A or 0.33mA

The current is therefore lower, which is (as Jeremy said) what is causing the transistor not to switch.

So, now we need to work out what resistor we need to replace the 10k ohm resistor.

We know V is now 3.3v, we know I was 0.0005A

R = V/I R = 3.3/0.0005 R = 6600 Ohms or 6k6 Ohms.

So, now it's just a case of replacing the 10k Ohm resistor for a 6k6 ohm resistor.