DRV110EVM: DRV110EVM: Help controlling solenoid

I'm using the DRV110EVM setup above with a TTL signal generator (1 Hz) into the Enable pin.    I'm trying to drive a bank of six 12vdc solenoid valves  (29 ohm each) connected in parallel  (4.8 ohm to the DRV110).  I can barely drive one valve with 14vdc supply.   I tried using a Solid State Relay (SSR) but its turn-on and turn-off speed is too slow to effectively pass the PWM pulses.

What must I do to drive at least  two or three of my solenoid valves?  I have attached images of my setup.

Is it possible to use a faster SSR to drive the bank of six valves?

Thanks for your help,

Ken

 

Hi Ken,

First we need to find out what are the valve requirements: Ipeak, Ihold and Tkeep.
The max Ipeak is < Vs/29ohm, that's less than 0.4A for Vs=12V
First experiment I'll recommend is to find out Ipeak needed:
1) Set Vs=14V
2) Set Rpeak=150kohm to get Ipeak=0.4A
3) Set Enable freq >5Hz to get Enable time <100mS, only Ipeak will be on without Ihold.
If it doesn't work, increase Vs and Ipeak up to 0.85A without changing Tkeep. Also you can increase Tkeep( increasing Ckeep) with 0.4A<Ipeak<0.85A
After finding out valve Ipeak and Tkeep, next step is to find out Ihold needed.
1) Enable_Ton> Tkeep
2) Adjust Ihold with Rhold, the max Ihold you can is 0.15A with EVM Rsense=1ohm.
If more Ihold current is needed you'll have to lower Rsense, my suggestion is Rsense=0.5ohm

After one valve works, Rsense needs to be adjusted to drive more valves
Rsense=previous Rsense/# valves

Regards,
Costin

Hi Ken,

Do you have any updates? One solenoid works with Ipeak=0.4A( Rsense=1ohm, Rpeak=150kohm)?
If you need to increase Vs >14V, series resistance is needed since DRV110 input zener turns on. Use EVM R3 as input current limiting resistor.
For your application SSR is not needed, the EVM FET has the required current capabilities.

Regards,
Costin
Costin

Costin,

Sorry for the late reply, very busy here.  I did check a single valve connected to the DRV110EVM.

I adjusted Rpeak = 150kohm and Vs=14vdc.

Using a Fluke 179,   I measured Ipeak = 0.38A and Ihold = 0.057A for a single valve.

Questions:

- Now should I need to reduce Rsense?  I will need to order a 1ohm resistor (in parallel to existing sense resistor).  Can I install a pot?

- Will the final pcba setup allow me to use one valve or six valves without adjusting Rsense or pts?

Thanks for your help,

Ken

Hi Ken,

For Rsense= 1ohm, the max Ipeak and Ihold is not enough to drive multiple solenoids:

Rsense range:

50mV/Ihold<Rsense<150mV/Rsense

300mV/Ipeak<Rsense<900mV/Ipeak

Pot is ok, the only issue I can think about is the price

Regards,

Costin