I have both and the only thing i see that would make a difference to me is range and price,i like the range of the ms20,but it is farther than the flash will reach,but the price is worth it to me.
As far as false pics,ive had none yet but im sure i will.others can answer you better than me though.
If i had it to do over i think i'd go with the RS or Lamson for the 9V low current draw. Having said that I'm in no way dissapointed with the MS20 and have had very good luck with it. I bought a bunch of the 1212 re-chargeable 12v batt's from Allelectronics for $7 ea and they work well, even in cold weather. It's tempting to go with the MS20 for price but after you've used the cam for a while you'll probably want for the 9V battery...Kinda a toss-up i guess since they all seem to work well.
I like the fact that you can tape off the light sensor and put it in test mode on the ms20 to make it not go through a roll of film in a 1/2 hour like the RS pir. I have one of each now and the RS performed flawlessly, I'm still finishing up my other with the MS20 and so far have only bench tested it. I'm waiting on my Allelectronics.com 12v batteries which are $10.50 now.
I also have 2 more cameras coming from Ebay....I'll probably go the ms20 on those also.
Dbworld - $10.50? Glad i bought mine when I did. Just a note of caution to ya, the Powersonic are around $14 off the shelf around here but they are new and fresh. I found that some of the 1212 batt's i've gotten from Allelectronics had old date codes (1998 and 1999). I had 2 that wouldn't take a charge at all but never returned them due the expense of shipping them back. Not bad out of 20 batt's but since the price is starting to get up there if you can get "new" ones for $14 you might be better served.
Wolf - the MS20 will run off of a 9V battery but it draws around 1.6ma at idle and will suck the life out of a 9V alkaline fairly quickly. Those 9V re-chargeables would work good though.
I use both PIR's. These are MY observations. The RS PIR works the best in the South during the summer when the temps get up to 100 deg's. There are VERY few false pics. They also work great in the winter. They are easy to modify and last me about 25+ days with a 9v battery. The MS20 will produce more false pics, especially in the summer. Careful placement of these will reduce these falsies. The MS20 is cheaper in price and more adaptable to different relay and battery schemes. My favorite so far, as directed by Tinhorn, is to use the 6v lantern battery with a 5v relay. This will last 100++ days. If you do the math, a 9v batttery setup lasts about 10 days at a minimum $2.84 apiece. At $6.54 a 6v battery, I get way over 10 times the life for about $25 bucks less. I can afford that! Also, the $ saved with the MS20 will buy you a Joe D. timer (which is an outstanding timer) or any other timer you want to build. I will probably keep using the MS20 PIR just for these reasons. I can live with a couple of false pics in the summer when I have the fewest cams out anyway. Just my 25 cents worth (inflation).
I like the ease of the RS pir,I am currently working on a couple of MS20s though,I am installing JOED's timers on both 1 long time and 1 short time chip.I have 2 more chips from joe that I will probably hook through a RS pir just to check out the results.
Don't forget the LAMSON PIR,it is just as easy to Mod as the RS and with Gunn Docc's timer work flawlessly,also hav 20 feet more than the RS
Really,you can't go wrong with any of them
my 37.5 cents worth (Canadian equvilant to US quarter)
I've been testing my MS20 with a 9 volt battery and it works fine. But can tell it's draining the battery already.
I thought I read on jesses homebrew page that the 9v rechargables didn't provide enough power. Just something I remember reading.
Never thought about false readings from the ms20. I've had 0 false readings with the RS pir. I make a point of facing them north though. Here in Michigan, this time of year, that guarentees no sunrises /sunsets to false trigger.
Where can I get the Powersonic batteries? Are these rechargable (I'm assuming yes).
Since we are on the subject....I bought a 6v motorcycle battery cheap at the Local Meijers recently. Will that work OK on the MS20 with a 5v relay? Or are there issues that I need to be concerned about?
The powersonic is the name brand for the re-chargeable PS1212 (and many others) 12V 1.2Amp Gel(lead-acid) battery. The batt's from Allelectronics are the same in size and capacity, i just think when i was buying them for $7.50ea they may have been a little dated.
I think what you read about the 9V re-chargeables applies to the little 9V batt's that look like the 9V alkalines. The large 9V re-chargeables, like Makita cordless drill batts, will work good.
I never did the 6V setup like Possum and Tinhorn but if you have the room for the 6V Lantern battery then it would be a very good option.
There are MANY ways to hook these things up and the MS20, RS, and Lamson are all very good PIR's for the application. I've recently built a couple with the Lamson 9V that are out now as we speak.
The 6v lantern battery was a tight fit for the smaller ammo cases, but I did get it in. The motorcycle 6v battery would probably be higher in amp hours and give you a katrillion days of use, except the cost would probably be higher. Remember, with the MS20 all you have to do is match the relay to the battery you are using. I agree, all the PIR's are good depending on the area, usage, placement, etc...