12v to 5v blower output


 
Steve_M

Steve_M

TVWBB Guru
I'm pretty sure this will work, I'm just looking for someone else to bounce this off of.

Rather than using a 12v blower, I'm going to be using an SSR which can be run at 5v. So rather than do 12v > 5v > 3.3v on the HM, I'm just going to power it with beefy 5v PSU for the HM and RasPi and let the IC4 3.3v regulator power the arduino.

From what I can tell, if I jumper the the 5v rail to the 12v rail, I should get 5v out of the blower circuit in pulse mode.

Correct?
 
I thought I explained why. I’m driving a solid state relay (SSR) not a blower. The SSR can take 3-32v. This removes any need for 12v on the system, so my quest is to send 5v to the blower output rather than 12v.
 
John, questions are the enemy to progress! ;)

I've got a nice 5v PSU for this project and don't see the need for using 12v when 5v is all that's needed.
 
Yes, just confirmed, feed the HM 5V and the blower output will scale 0-5V.
Everything besides the blower runs on 5 or 3.3v, and the blower circuit just scales from 0V to the supply voltage (be it 5 or 15)
 
Yeah you can just jumper the 5V and 12V pins where the 5V regulator is supposed to be (don't use it at all). If you feed in from the barrel jack, remember that there's a diode in the path as well which is going to drop your "5V" output at the output connector down to around 4.5V-4.7V. The "12V" output will be directly fed from the input voltage though and be a roughly 5V PWM (if PWM mode is selected obviously)

If you're doing an SSR only, I'd recommend leaving off the inductor (short its two pads together) and the 47uF/25V capacitor (leave it off) to get a sharper PWM output.
 
Also verify that the SSR actually works reliably at 5v. Most of the cheap Chinese ones I've gotten don't reliably work at 5V even though they are spec'd for 3.2v to 32v.

I've never had an issue with Crydom brand, but they cost ~7x as much and the Chinese ones.

david
 
Bryan Mayland said:
Yeah you can just jumper the 5V and 12V pins where the 5V regulator is supposed to be (don't use it at all). If you feed in from the barrel jack, remember that there's a diode in the path as well which is going to drop your "5V" output at the output connector down to around 4.5V-4.7V. The "12V" output will be directly fed from the input voltage though and be a roughly 5V PWM (if PWM mode is selected obviously)

If you're doing an SSR only, I'd recommend leaving off the inductor (short its two pads together) and the 47uF/25V capacitor (leave it off) to get a sharper PWM output.
Click to expand...

Perfect. Thanks, Bryan!
 
You must log in or register to reply here.

 

Back
Top