New Open Source Valentine One USB Adapter Design

**PredatorCoder** · 07-27-2007, 06:56 PM

Originally Posted by Madmac

One small point looking at your schematic. The pchan fet will be partly turned on by connecting the the microcontroller pin. The Vgs for the IRFR9024 starts to turn the device on at 4.5volts. The AT90USB162 (have not used this part) port pin will have a protection network to VCC (even if configured as an open drain output). That will give 7'sh volts on the gate.

Good catch! I think I was half-asleep when I did that part. You are right. And I found another issue: that transistor can only do a maximum gate-to-source voltage of -20 volts. Which means that if your Valentine One is on (microcontroller output is pulled to ground) and your alternator does a load dump, you are theoretically screwed since you will likely exceed -20 volts. So if using MOSFET, one needs one with greater Vgs maximum rating. And when Valentine One is supposed to be off (microcontroller output is 5V) then Vgs is still -7 volts. So it won't actually turn off, as you noted. That could be worked-around by tri-stating the microcontroller output, except that I suppose you have to find a way to remove the charge on the MOSFET's gate.

Perhaps a PNP transistor would be a better choice? To turn the Valentine One off, one could tri-state the microcontroller output and then nothing will be driving current into the transistor, at which point no current will be allowed into the V1.

Originally Posted by Road_Dog

In my Grand Amm yes. Others....no.

That does make for a tricky thing... Yes you will be forced to use a battery or run a +12V power line up there (as well as ground). Charging the battery will be a challenge. Best thing I can think of would be something solar on the back of the mirror. Otherwise you are stuck periodically plugging a charger into your mirror. I guess you have to choose which of those options is the least unsightly. Remember your battery has to sustain a 425 mA load going to the V1 and also supply current to the Bluetooth radio.

**Madmac** · 07-29-2007, 07:36 AM

Because the micro I/O port is also configurable as input it will have a protection network to Vcc. So if you use a PNP bipolar device you will still have the problem. Only real solution is to add a device to level shift. A low cost signal fet
with the power fet connected by a resistor. Use a resistor between gate and source on the power fet to make sure it is off when it should be and put a 10V zener across it to protect the power fet for Vgs max. Extra parts 1 x low power fet, 2 x resistors, 1 x 10V zener. There are many other ways to do it, the above only adds a few cents to to BOM.
It is usual to design for worst case (during power dump) of 80V.

**Hedge** · 08-01-2007, 04:31 PM

Has anyone removed the sensors from a Valentine One for remote placement?

Having the unit completely hidden with this interface and only the sensors stuck to the front and rear windshields would be sweet.

**PredatorCoder** · 08-03-2007, 07:49 PM

Originally Posted by Hedge

Has anyone removed the sensors from a Valentine One for remote placement?

Having the unit completely hidden with this interface and only the sensors stuck to the front and rear windshields would be sweet.

From what I have heard elsewhere on forums, this is extremely non-trivial if not impossible. It would likely require significant re-engineering of the V1 as the sensors are all integrated onto one PCB/block.

Best solution for front/rear sensing would be two V1s (expensive, I know, but probably necessary). Using two of the discussed USB adapters you could potentially combine their alerts on a PC. Each unit could be hidden in the front and rear of the vehicle. This is probably not worth the trouble unless the V1 is illegal where you live. I have a friend in Virginia who knows someone who put a single V1 underneath the front of the vehicle (i.e. don't go over too big a bump). Detectors are illegal in VA, but cops aren't finding that... However that person only has one V1, so rear detection is not really possible - too much metal for the rear sensor to go through.

**cventers** · 08-25-2007, 02:04 AM

Looks great! I'm pretty useless with hardware but if I could buy such a piece I might be able to find the time to develop a Linux driver.

**tkn** · 08-28-2007, 12:31 PM

Originally Posted by PredatorCoder

From what I have heard elsewhere on forums, this is extremely non-trivial if not impossible. It would likely require significant re-engineering of the V1 as the sensors are all integrated onto one PCB/block.

Best solution for front/rear sensing would be two V1s (expensive, I know, but probably necessary). Using two of the discussed USB adapters you could potentially combine their alerts on a PC. Each unit could be hidden in the front and rear of the vehicle. This is probably not worth the trouble unless the V1 is illegal where you live. I have a friend in Virginia who knows someone who put a single V1 underneath the front of the vehicle (i.e. don't go over too big a bump). Detectors are illegal in VA, but cops aren't finding that... However that person only has one V1, so rear detection is not really possible - too much metal for the rear sensor to go through.

Yeah, I looked into it years ago. I would just love to take it apart and just mount the sensors in appropriate places, but the general consensus was to just buy 2. I gave up, mounted it pretty low and sacrificed rear detection for the most part.

Eventually I will probably tear apart one of the visors and install the detector in there.

**iamgnat** · 01-03-2008, 09:11 PM

Any news on this or source release?

I'm looking at building a Atmel (ATMega series) based interface using the FTDI DLP-USB232M USB->Serial module.

Any chance you got your AVR code to a point you're willing to post it yet?

Thanks,
-dave

**Beehphy** · 01-07-2008, 11:53 AM

Originally Posted by tkn

Yeah, I looked into it years ago. I would just love to take it apart and just mount the sensors in appropriate places, but the general consensus was to just buy 2. I gave up, mounted it pretty low and sacrificed rear detection for the most part.

Eventually I will probably tear apart one of the visors and install the detector in there.

Unfortunately the reason they built the sensors into that bolck is to shield unwanted RF. the signals from the sensor are'nt that big, which makes them suseptable to RF interferance.

It would take a serious redesign to move the sensors and amplifiers out of the main body so that the signals from the sensor to the "brain" were large enough to be imune to noise.

The idea of moving the whole unit to the grille and using a remote display is way more feasable.

**creaseguard** · 05-17-2008, 06:38 AM

Any status on this project?

Jay

**MattJackson86** · 05-18-2008, 01:14 PM

I dont know about the status of this project, but I am currently in the process of creating my own interface. I know the design I am going for and am in the process of prototyping it. I am planning on this version being a serial connection (easy enough to go to USB later) and will allow retrieval of the V1 info. I am also hoping that it will be able to mute/change mode/turn display on & off via software (but this will be worked out during the prototype). I will be posting here (or a new thread) on my status.